Earth’s oceans contain 97% of the planet’s water, so just 3% is fresh water, water with low concentrations of salts. Most fresh water is trapped as ice in the vast glaciers and ice sheets of Greenland.

A water molecule may pass through a reservoir very quickly or may remain for much longer. The amount of time a molecule stays in a reservoir is known as its residence time.Earth’s oceans contain 97% of the planet’s water, so just 3% is fresh water, water with low concentrations of salts.

A storage location for water such as an ocean, glacier, pond, or even the atmosphere is known as a reservoir. A water molecule may pass through a reservoir very quickly or may remain for much longer.

Because of the unique properties of water, water molecules can cycle through almost anywhere on Earth. The water molecule found in your glass of water today could have erupted from a volcano early in Earth history.

The molecule surely was high up in the atmosphere and maybe deep in the belly of a dinosaur. Where will that water molecule go next.

Along with that, Earth is the only planet where water is present in all three states. Because of the ranges in temperature in specific locations around the planet, all three phases may be present in a single location or in a region.

Because Earth’s water is present in all three states, it can get into a variety of environments around the planet. The movement of water around Earth’s surface is the hydrologic (water) cycle.The Sun, many millions of kilometers away, provides the energy that drives the water cycle.

The oceans are discussed in detail in the chapter Earth’s Oceans. Water changes from a liquid to a gas by evaporation to become water vapor.

Only the water molecules evaporate. the salts remain in the ocean or a freshwater reservoir.

The droplets gather in clouds, which are blown about the globe by wind. As the water droplets in the clouds collide and grow, they fall from the sky as precipitation.

Sometimes precipitation falls back into the ocean and sometimes it falls onto the land surface. This animation shows the annual cycle of monthly mean precipitation around the world.

When water falls from the sky as rain it may enter streams and rivers that flow downward to oceans and lakes. Water that falls as snow may sit on a mountain for several months.

Snow and ice may go directly back into the air by sublimation, the process in which a solid changes directly into a gas without first becoming a liquid. Although you probably have not seen water vapor sublimating from a glacier, you may have seen dry ice sublimate in air.

Snow and ice slowly melt over time to become liquid water, which provides a steady flow of fresh water to streams, rivers, and lakes below. A water droplet falling as rain could also become part of a stream or a lake.

A significant amount of water infiltrates into the ground. Soil moisture is an important reservoir for water.

Water may seep through dirt and rock below the soil through pores infiltrating the ground to go into Earth’s groundwater system. Groundwater enters aquifers that may store fresh water for centuries.

Plants and animals depend on water to live and they also play a role in the water cycle. Plants take up water from the soil and release large amounts of water vapor into the air through their leaves, a process known as transpiration.

Not content to get water directly from streams or ponds, humans create canals, aqueducts, dams, and wells to collect water and direct it to where they want it. The table above displays water use in the United States and globally (Estimated Use of Water in the United States in 2005, USGS).

If climate cools and glaciers and ice caps grow, there is less water for the oceans and sea level will fall. The reverse can also happen.

1 Distribution of Freshwater and Saltwater. 2 How is Earth’s water distributed among saltwater and freshwater Earth is known as the “blue planet” because over 70% of Earth’s surface is covered with water.

Most of Earth’s freshwater is found in the polar ice caps near the North and South Poles. Most of Earth’s freshwater is found in the polar ice caps near the North and South Poles.

From largest to smallest, the amounts of water on Earth are salt water (97%), solid fresh water (2%), liquid fresh water (1%).

From largest to smallest, the amounts of water on Earth are salt water (97%), solid fresh water (2%), liquid fresh water (1%).

Oceans contain salt water. In order of size from largest to smallest, Earth’s oceans are the Pacific, Atlantic, and Indian Oceans.

5 Fresh Water Most of the Earth’s freshwater is located in the polar caps (ice). Most of the Earth’s freshwater is located in the polar caps (ice).

Underground water, lakes, rivers, and glaciers hold the rest of Earth’s surface freshwater. The largest portion of the Earth’s liquid freshwater is trapped between underground layers of rock.

The largest portion of the Earth’s liquid freshwater is trapped between underground layers of rock. This trapped freshwater is called groundwater.

A glacier is a very slow moving river of ice.

All living things share less than 1% of total water on Earth.

8 Groundwater.

Beijing is sinking. In some neighborhoods, the ground is giving way at a rate of four inches a year as water in the giant aquifer below it is pumped.

Beijing, despite tapping into the gigantic North China Plain aquifer, is the world’s fifth most water-stressed city and its water problems are likely to get even worse. Beijing isn’t the only place experiencing subsidence, or sinking, as soil collapses into space created as groundwater is depleted.

Sections of California’s Central Valley have dropped by a foot, and in some localized areas, by as much as 28 feet. Around the world, alarms are being sounded about the depletion of underground water supplies.

About 30 percent of the planet’s available freshwater is in the aquifers that underlie every continent. More than two-thirds of the groundwater consumed around the world irrigates agriculture, while the rest supplies drinking water to cities.

Now, the world’s largest underground water reserves in Africa, Eurasia, and the Americas are under stress. Many of them are being drawn down at unsustainable rates.

Richard Damania, a lead economist at the World Bank, predicts that without adequate water supplies, economic growth in the most stressed parts of the world could decline by six percent of GDP. His findings conclude that the most severe impacts of climate change will deplete water supplies.

Run-off is declining,” he says. “People are turning to groundwater in a very, very big way.”.

In the United States, farmers are withdrawing water at unsustainable rates from the High Plains, or Ogallala Aquifer, even though they have been aware of the threat for six decades. Over the past three decades, Saudi Arabia has been drilling for a resource more precious than oil.

They are tapping into the aquifer at unsustainable rates. On these NASA satellite images of the Wadi As-Sirhan Basin, green indicates crops, contrasting with the pink and yellow of dry, barren land.

Given that these guys are earning so little, there is very little you can do to control it,” Damania says. “And you are, literally, in a race to the bottom.”.

Unrest in Yemen, which heavily taps into groundwater and which experienced water riots in 2009, is rooted in a water crisis. Experts say water scarcity also helped destabilize Syria and launch its civil war.

Jay Famiglietti, lead scientist on a 2015 study using NASA satellites to record changes in the world’s 37 largest aquifers, says that the ones under the greatest threat are in the most heavily populated areas. “Without sustainable groundwater reserves, global security is at far greater risk,” he says.

The implications are just staggering and really need to be discussed at the international level.”. Below are answers to your key questions.

The Indus Basin aquifer in northwest India and Pakistan is the second-most threatened, and the Murzuk-Djado Basin in northern Africa the third. The 20 million people of Beijing get about two-thirds of their water from the North China Plain aquifer, which is one of the world’s largest groundwater basins.

Flood irrigation, which is inefficient, remains the dominant irrigation method worldwide. In India, the world’s largest consumer of groundwater, the government subsidizes electricity – an incentive to farmers to keep pumping.

Irrigation has enabled water-intensive crops to be grown in dry places, which in turn created local economies that are now difficult to undo. These include sugar cane and rice in India, winter wheat in China, and corn in the southern High Plains of North America.

Groundwater is cold enough to raise cold-water fish, such as trout and sturgeon. In less than two decades, the aquifer there has been drawn down so severely for fish ponds that municipal water supplies in more than two dozen communities are now threatened.

Calculating what remains in aquifers is extraordinarily difficult. In 2015, scientists at the University of Victoria in British Columbia, Canada concluded that less than six percent of groundwater above one-and-a-half miles (two kilometers) in the Earth’s landmass is renewable within a human lifetime.

More important is how the water is distributed throughout the aquifer. When water levels drop below to 50 feet or less, it is often not economically practical to pump water to the surface, and much of that water is brackish or contains so many minerals that it is unusable.

In Western Australia, desalinated water has been injected to recharge the large aquifer that Perth, Australia’s driest city, taps for drinking water. China is working to regulate pumping.

Most water in Earth’s atmosphere and crust comes from saline seawater, while freshwater accounts for nearly 1% of the total. The vast bulk of the water on Earth is saline or salt water, with an average salinity of 35‰ (or 3.5%, roughly equivalent to 34 grams of salts in 1 kg of seawater), though this varies slightly according to the amount of runoff received from surrounding land.

Saline groundwater is seldom considered except when evaluating water quality in arid regions.

Typically, fresh water is defined as water with a salinity of less than 1 percent that of the oceans – i.e. below around 0.35‰.

The ratio of salt water to fresh water on Earth is around 50 to 1.

Although in warm periods such as the Mesozoic and Paleogene when there were no glaciers anywhere on the planet all fresh water was found in rivers and streams, today most fresh water exists in the form of ice, snow, groundwater and soil moisture, with only 0.3% in liquid form on the surface. Of the liquid surface fresh water, 87% is contained in lakes, 11% in swamps, and only 2% in rivers.

Although the total volume of groundwater is known to be much greater than that of river runoff, a large proportion of this groundwater is saline and should therefore be classified with the saline water above. There is also a lot of fossil groundwater in arid regions that have never been renewed for thousands of years.

The total volume of water on Earth is estimated at 1.386 billion km³ (333 million cubic miles), with 97.5% being salt water and 2.5% being freshwater. Of the freshwater, only 0.3% is in liquid form on the surface.

Because the oceans that cover roughly 70.8% of the area of Earth reflect blue light, Earth appears blue from space, and is often referred to as the blue planet and the Pale Blue Dot. Liquid freshwater like lakes and rivers cover about 1% of Earth’s surface and altogether with Earth’s ice cover, Earth’s surface is 75% water by area.

Collectively, Earth’s lakes hold 199,000 km3 of water. Most lakes are in the high northern latitudes, far from human population centers.

The Great Lakes Basin is home to 33 million people. The Canadian cities of Thunder Bay, St.

cities of Detroit, Duluth, Milwaukee, Chicago, Gary, Cleveland, Buffalo, and Rochester are all located on shores of the Great Lakes System.

Its distribution is broadly similar to that of surface river water, but it is easier to store in hot and dry climates because groundwater storage are much more shielded from evaporation than are dams. In countries such as Yemen, groundwater from erratic rainfall during the rainy season is the major source of irrigation water.

Because groundwater recharge is much more difficult to accurately measure than surface runoff, groundwater is not generally used in areas where even fairly limited levels of surface water are available.

The total volume of water in rivers is estimated at 2,120 km3 (510 cu mi), or 0.49% of the surface fresh water on Earth. Rivers and basins are often compared not according to their static volume, but to their flow of water, or surface run off.

There can be huge variations within these regions. For example, as much as a quarter of Australia’s limited renewable fresh water supply is found in almost uninhabited Cape York Peninsula.

The areas of greatest concentration of renewable water are:.

Variability of water availability is important both for the functioning of aquatic species and also for the availability of water for human use: water that is only available in a few wet years must not be considered renewable. Because most global runoff comes from areas of very low climatic variability, the total global runoff is generally of low variability.

Indeed, even in most arid zones, there tends to be few problems with variability of runoff because most usable sources of water come from high mountain regions which provide highly reliable glacier melt as the chief source of water, which also comes in the summer peak period of high demand for water.

However, in Australia and Southern Africa, the story is different. Here, runoff variability is much higher than in other continental regions of the world with similar climates.

The reason for this is that, whereas all other continents have had their soils largely shaped by Quaternary glaciation and mountain building, soils of Australia and Southern Africa have been largely unaltered since at least the early Cretaceous and generally since the previous ice age in the Carboniferous.

proteoid roots) to absorb minimal phosphorus and other nutrients. Because these roots absorb so much water, runoff in typical Australian and Southern African rivers does not occur until about 300 mm (12 in) or more of rainfall has occurred.

The consequence of this is that many rivers in Australia and Southern Africa (as compared to extremely few in other continents) are theoretically impossible to regulate because rates of evaporation from dams mean a storage sufficiently large to theoretically regulate the river to a given level would actually allow very little draft to be used.

Even for other Australian rivers, a storage three times as large is needed to provide a third the supply of a comparable climate in southeastern North America or southern China. It also affects aquatic life, favouring strongly those species able to reproduce rapidly after high floods so that some will survive the next drought.

Tropical (Köppen climate classification A) climate rivers in Australia and Southern Africa do not, in contrast, have markedly lower runoff ratios than those of similar climates in other regions of the world. Although soils in tropical Australia and southern Africa are even poorer than those of the arid and temperate parts of these continents, vegetation can use organic phosphorus or phosphate dissolved in rainwater as a source of the nutrient.

There are other isolated areas of high runoff variability, though these are basically due to erratic rainfall rather than different hydrology. These include:.

It has been hypothesized that the water is present in the Earth’s crust, mantle and even the core and interacts with the surface ocean through the “whole-Earth water cycle”. However, the actual amount of water stored in the Earth’s interior still remains under debate.

The lower mantle of inner earth may hold as much as 5 times more water than all surface water combined (all oceans, all lakes, all rivers).

Glaciers exist on every continent except Australia. Approximate distribution is:91% in Antarctica8% in GreenlandLess than 0.5% in North America (about 0.1% in Alaska)0.2% in AsiaLess than 0.1% are in South America, Europe, Africa, New Zealand, and Indonesia.

Approximate distribution is:91% in Antarctica8% in GreenlandLess than 0.5% in North America (about 0.1% in Alaska)0.2% in AsiaLess than 0.1% are in South America, Europe, Africa, New Zealand, and Indonesia. Mount Rainier, Washington, at 14,410 feet (4,393 meters), the highest peak in the Cascade Range, is a dormant volcano whose glacier ice cover exceeds that of any other mountain in the conterminous United States.

It contains more than five times the glacier area of all the other Cascade volcanoes combined. Mount Baker (Washington) at 10,778 feet (3,285..

Mount Rainier has approximately 26 glaciers. It contains more than five times the glacier area of all the other Cascade volcanoes combined.

The age of the oldest glacier ice in Antarctica may approach 1,000,000 years old The age of the oldest glacier ice in Greenland is more than 100,000 years old The age of the oldest Alaskan glacier ice ever recovered (from a basin between Mt. Bona and Mt.

Glacier flow moves newly formed ice through the entire length of a typical Alaskan valley glacier in 100.. The age of the oldest glacier ice in Antarctica may approach 1,000,000 years old The age of the oldest glacier ice in Greenland is more than 100,000 years old The age of the oldest Alaskan glacier ice ever recovered (from a basin between Mt.

Churchill) is about 30,000 years old. Glacier flow moves newly formed ice through the entire length of a typical Alaskan valley glacier in 100..

Most U.S. glaciers are in Alaska.

Utah’s Timpanogos Glacier is now a rock glacier (in which the ice is hidden by rocks), and Idaho’s Otto Glacier has melted away. Canada has glaciers in Alberta..

Most U.S. glaciers are in Alaska.

Utah’s Timpanogos Glacier is now a rock glacier (in which the ice is hidden by rocks), and Idaho’s Otto Glacier has melted away. Canada has glaciers in Alberta..

Learn more: USGS Water Science School: Glaciers and Icecaps National Snow and Ice Data Center: Facts about Glaciers U.S. Global Change Research Program: Sea..

Learn more: USGS Water Science School: Glaciers and Icecaps National Snow and Ice Data Center: Facts about Glaciers U.S. Global Change Research Program: Sea..

“Global warming” refers to the rise in global temperatures due mainly to the increasing concentrations of greenhouse gases in the atmosphere. “Climate change” refers to the increasing changes in the measures of climate over a long period of time – including precipitation, temperature, and..

“Global warming” refers to the rise in global temperatures due mainly to the increasing concentrations of greenhouse gases in the atmosphere. “Climate change” refers to the increasing changes in the measures of climate over a long period of time – including precipitation, temperature, and..

Continual melt from glaciers contributes water to the ecosystem throughout dry months, creating perennial stream habitat and a water source for plants and animals. The cold runoff from glaciers also affects downstream water temperatures.

Some.. Glaciers act as reservoirs of water that persist through summer.

The cold runoff from glaciers also affects downstream water temperatures. Many aquatic species in mountainous environments require cold water temperatures to survive.

A glacier is a large, perennial accumulation of crystalline ice, snow, rock, sediment, and often liquid water that originates on land and moves down slope under the influence of its own weight and gravity. Typically, glaciers exist and may even form in areas where: mean annual temperatures are close to the freezing point winter precipitation produces significant accumulations of snow temperatures..

Typically, glaciers exist and may even form in areas where: mean annual temperatures are close to the freezing point winter precipitation produces significant accumulations of snow temperatures.. Earth is estimated to hold about 1,386,000,000 cubic kilometers of water.

Earth is estimated to hold about 1,386,000,000 cubic kilometers of water. The breakdown of where all that water resides is estimated as follows: Oceans (saline) 1,338,000,000 cubic kilometers Ice caps and glaciers (fresh) 24,064,000 cubic kilometers Groundwater (fresh and saline) 23,400,000 cubic kilometers Streams, lakes, swamps (fresh) 104,590 cubic kilometers Lakes (saline) 85,400 cubic..

As coastal development along the Gulf Coast continues to expand, tidal saline wetlands could have difficulty adjusting to rising sea levels. ANCHORAGE, Alaska — This year marks the 50th anniversary of one of the longest continuous glacier research efforts in North America.

The U.S. Geological Survey and Oregon State University released a report this week examining Pacific Northwest tidal wetland vulnerability to sea..

ANCHORAGE, Alaska Melting glaciers are not just impacting sea level, they are also affecting the flow of organic carbon to the world’s oceans..

Earth is the fifth largest planet in the solar system.

“That’s home. That’s us,” Sagan wrote.

Though the sheer size of Earth in metaphorical terms is immeasurable to humanity, the planet’s physical size can indeed be calculated. Related: How old is Earth.

Earth’s widest point is the equator, which runs across the planet’s center at zero degrees latitude. This is because Earth is not a perfect sphere.

According to NASA, Earth’s radius at the equator is 3,963 miles (6,378 kilometers), while the radius at the poles is 3,950 miles (6,356 km).

Again, because of the equatorial bulge, the planet’s diameter is slightly smaller when measured from pole to pole, where it is about 7,900 miles (12,712 km). The equatorial circumference of Earth is 24,901 miles (40,075 km).

That reveals that our planet is flattened at the poles, meaning its shape is an oblate spheroid.

Greek philosopher Aristotle is credited as the first person to have attempted to determine Earth’s circumference, according to NOAA. He calculated the distance around the planet to be about 45,500 miles (73,225 km).

Today, scientists measure Earth by improving on a method developed by another Greek polymath, Eratosthenes, around 250 B.C. Eratosthenes used trigonometry to determine the distance between Aswan and Alexandria by measuring the position of the sun at the same time in both locations.

This practice formed the basis of geodesy, the science of measuring Earth’s size and fundamental properties, such as its geometric shape, its orientation in space, and its gravity field. Earth bulges at the equator and is flattened at the poles as the result of force caused by the planet’s rotation.

Interestingly, the equatorial bulge means that the gravitational pull of Earth is slightly weaker at the equator than at the poles, making the equator the ideal location for space launches.

With these values known, and Earth’s oddball shape accounted for, it is easy to calculate the density of Earth, which is around 5.5 grams per cubic centimeter. The surface area of Earth is about 197 million square miles (510 million square kilometers).

The highest point on Earth’s surface in terms of altitude above sea level is the top of Mount Everest, which peaks at 29,029 feet (8,848 meters). The farthest point from Earth’s center is Mount Chimborazo, the summit of which is over 6,800 feet (2,073 m) farther from Earth’s center than Mount Everest’s summit is, according to the National Oceanic and Atmospheric Administration (NOAA).

Earth is the fifth-largest planet in the solar system, behind Jupiter, Saturn, Uranus and Neptune.

The gas giant has a volume of 343 trillion cubic miles (1,431 trillion cubic kilometers), meaning it would take around 1,320 Earths to fill the volume of Jupiter. According to NASA, if Earth were the size of a grape, Jupiter would be the size of a basketball.

With a diameter of 30,599 miles (49,244 km), Neptune — the fourth largest planet in the solar system —is around four times as wide as Earth. It would take 57 Earths to fill the volume of Neptune.

Although Earth is dwarfed by the outer planets, it is still the largest of the inner, rocky planets. Venus is the second largest rocky planet, followed by Mars and Mercury.

Earth and Mercury are the densest planets in the solar system, according to The Open University, with their densities similar to that of the iron-rich mineral hematite. The reason for Earth’s high density is its core, which has a diameter of around 7,000 miles (11,265 km) and is made of 80% iron and around 5% nickel and some lighter elements, such as carbon, oxygen, silicon, or sulfur.

We asked Simon Lock, a research fellow in the School of Earth Sciences at the University of Bristol who studies the dynamics of our planet, some questions about Earth’s size and how it compares with those of other worlds.

From the very center of the Earth to the surface [i.e., Earth’s radius] is 6,378 km (3,963 miles), the same distance from Kampala [Uganda] to Kolkata [India] or London to Chicago.

The smallest, Mercury, is only 40% the radius of Earth. However, Jupiter is 11 times bigger than Earth and is the largest planet in our solar system, with its rocky core buried deep within an envelope of hydrogen and helium gas.

This is a hard question and depends on what you consider to be Earth-like. Planets that have a similar mass and composition to Earth are likely relatively common in other solar systems, but the ones we have found so far are typically too close to their stars to host liquid water oceans.

In short, there are lots of things that make Earth such a special planet, and we do not know enough about planets around other stars to confidently say how many planets like ours there are out there in the galaxy. There are many ways that scientists try and understand the dynamics of Earth.

Others study the waves that come from earthquakes to image the inside of the planet, much like the way a CT scanner works, or measure how different materials behave at the high pressures and temperatures inside our planet.

Sometimes, this requires me to just sit down with a pen and paper and work through some math [and], at other times, to use some of the most powerful computers in the world. Most importantly, I spend a lot of time talking to other scientists, bouncing ideas off each other, and combining our knowledge to understand the workings of our dynamic planet.

Khan Academy explains the formation of our planet.

A NASA simulation replicates conditions across one of these “failed stars.”. Want to feel really small.

Densities of Solar System Planets, Open University, [accessed 10/20/23], [ Earth Fact Sheet, NASA, [accessed 10/20/23], [ How large is Earth. CalTech Cool Cosmos, [accessed 10/20/23], [ The History of Geodesy, NOAA, [accessed 10/20/23], [.

Lakes play a vital role in influencing the weather patterns and ecology of an area. All the world’s lakes together (more than a million) also have a significant effect on the global climate.

Scientists are also worried that climate change will have a dire impact on the lakes of the world. In some places, lakes will dry up while in others, new lakes will be formed.

Hence, scientists feel that an inventory of the current status lakes of the world needs to be created to monitor the changes and study their impact on the environment around us.

Knowing their numbers will help in monitoring them more efficiently. So, geographers from McGill University, Canada, conducted a study on the lakes of the world and prepared a list of 10 countries with the largest number of lakes.

km (10 hectares) or larger were taken into account. The study was published in Nature Communications in 2016.

According to the study, the 10 countries with the most lakes in the world are:. The study showed that most of the areas or countries with high lake densities are located in the northern parts of the Northern Hemisphere like Northern Canada, Scandinavia, Russia and Alaska.

The retreat of glaciers at the end of the Ice Age left behind hundreds of thousands of lakes that we see today.

Here glacial action and tectonic shifts lead to lake formations. Large floodplains of rivers like the Amazon River in Brazil and the coastal rivers of China also result in numerous lakes.

According to the study, Canada is home to the largest number of lakes in the world. Of the 1.42 million lakes around the world with a size of over 0.1 sq.

These lakes play a very significant role in shaping the water cycle of the country. However, very little is known about most of these lakes.

Old lakes might drain out and new ones form. Hence, studying these lakes in detail becomes necessary.

It is no surprise that most of the US states with the greatest number of lakes are found in the northern part of the country. It is the part that has experienced the most active glacial movement in the recent past.

Minnesota, however, has the most named lakes in the country.

However, there are many articles stating that Finland has 187,888 lakes and that makes it the country with the most lakes in relation to the size of the country. In fact, it is estimated that Finland has one lake for every 26 persons.

There is no standard unambiguous definition of the size requirements for a water body to be classified as a lake.

m or just a little larger than the size of a basketball court. However, the list in the study was prepared by taking into account only lakes that are over 0.1 sq.

m in size which is the size of about 18.5 football fields. Hence, Finland failed to feature on this list.

The hunt for water on Mars has always been a point of interest for researchers. Earth has life almost everywhere water exists.

And if Mars is to become a future home, knowing where water exists will be necessary for our survival. Both NASA and the European Space Agency (ESA) have special instruments searching for water on the red planet.

Many people know Mars as a dry and dusty planet, but it hasn’t always been that way. Approximately 4.1 to 3.8 billion years ago, Mars had a massive ocean called Oceanus Borealis.

Specific planetary conditions at that time let water exist on its surface. Changes in temperature, climate, and geology over the years gradually pushed water out to the atmosphere or into the ground.

Hydrous minerals are essentially rocks that have water (or its two main elements, hydrogen and oxygen), incorporated into their chemical structure.

While these minerals look pretty similar to the naked eye, their chemical compositions and structural arrangements vary. They are detectable by sophisticated equipment and can tell scientists how water geologically changes over time.

It is a geological map of the rocks that are holding what remains of Mars’s ancient ocean. Despite being a “graveyard” for the bulk of the planet’s ocean, hydrous minerals are not the only source of water on Mars.

The northern polar ice cap contains the only visible water on the planet, while the southern pole covers its water with a frozen carbon-dioxide cap. In 2020, radar analyses suggested the presence of liquid water, potentially part of a network of underground saltwater lakes, close to the southern pole.

More frozen water may be locked away in the deep subsurface, far below what current surveying equipment is able to inspect. The new water map is highlighting areas of interest for future exploration on Mars.

Finding where they co-exist with known areas of buried frozen water provides possible opportunities for extracting water. ESA’s Rosalind Franklin Rover will land in Oxia Planum, a region rich in hydrous clays, to investigate how water shaped the region and whether life once began on Mars.

We are focused on the benefits of purified water but, perhaps, we don’t take time to reflect on the remarkable nature of water itself. It is no exaggeration to suggest its unique properties make possible the world in which we live.

It has a high specific heat, heat of vaporisation and surface tension. It is highly cohesive and adhesive with a solid form which is less dense than the liquid.

As shown in the diagram, the two hydrogen atoms are 95.8 pm from the oxygen atom and located on the same side 104.5° apart. The hydrogen atoms are positively charged while the oxygen atom is negatively charged, resulting in a strongly dipolar molecule.

Water molecules are continuously moving and hydrogen bonds are breaking and reforming but hydrogen bonding is strong enough to be responsible for most of the unusual properties as described below: The increased attraction between water molecules raises its boiling point, making it a liquid at room temperature unlike its close neighbours in the periodic table which are all gases (H2S, NH3, HF).

These make water a good coolant in the laboratory and elsewhere, but, more generally and importantly, buffers global temperature changes. As it cools thermal motion is reduced enabling more hydrogen bonds to form and preventing water molecules from coming closer together.

As the ice melts and the water warms hydrogen bonds are broken enabling the molecules to pack more densely up to 4°C when water is at its most dense. At higher temperatures increased thermal motion causes the water to expand and become less dense.

It freezes from the top, leaving denser sub-surface water at about 4°C. The ice then also acts as an insulator.

These species in water become surrounded by a hydration sphere of water molecules with, for example, the negatively charged end of the water molecule attracted to the positive ion or part of the solute molecule. This enables the solid lattice to be disrupted and the material to dissolve.

This combination also results in capillary action, in which water rises in a narrow tube against the force of gravity. These effects also have considerable biological significance.

This accounts for the residual electrical conductivity of ultrapure water of 0.055 µS/cm (equivalent to a resistivity of 18.15 MΩ.cm). In practice, the conductivity of water in the environment is always higher and is dependent on the ions dissolved in it.

Dr Paul Whitehead. After a BA in Chemistry at Oxford University, Paul focused his career on industrial applications of chemistry.

He spent the first half of his career managing the analytical support team at the Johnson Matthey Research/Technology Centre,specialising in the determination of precious metals and characterising applications such as car-exhaust catalysts and fuel cells. Subsequently, as Laboratory Manager in R&D for ELGA LabWater, he has been involved in introducing and developing the latest water purification technologies.

the Fresh ecosystem The freshwater ecosystem includes lakes, ponds, rivers, and stream. Lakes are bodies of fresh water surronded by land, while ponds are smaller bodies of water.

Rivers and streams are moving bodies of freshwater. They usally originate in mountains and come from melting ground water and eventually flow into the ocean 97% of Earth’s water is saltwater leaving around 3% of Earth’s water as Freshwater.

No two freshwater biomes are exactly the same. Freshwater biomes contain plenty of grass and plants but trees are very scarce.There are many insects living in the freshwater biome that some might consider being pests including mosquitos and flies.

the Fresh ecosystem The freshwater ecosystem includes lakes, ponds, rivers, and stream. Lakes are bodies of fresh water surronded by land, while ponds are smaller bodies of water.

Rivers and streams are moving bodies of freshwater. They usally originate in mountains and come from melting ground water and eventually flow into the ocean 97% of Earth’s water is saltwater leaving around 3% of Earth’s water as Freshwater.

No two freshwater biomes are exactly the same. Freshwater biomes contain plenty of grass and plants but trees are very scarce.There are many insects living in the freshwater biome that some might consider being pests including mosquitos and flies.

the Fresh ecosystem The freshwater ecosystem includes lakes, ponds, rivers, and stream. Lakes are bodies of fresh water surronded by land, while ponds are smaller bodies of water.

Rivers and streams are moving bodies of freshwater. They usally originate in mountains and come from melting ground water and eventually flow into the ocean 97% of Earth’s water is saltwater leaving around 3% of Earth’s water as Freshwater.

No two freshwater biomes are exactly the same. Freshwater biomes contain plenty of grass and plants but trees are very scarce.There are many insects living in the freshwater biome that some might consider being pests including mosquitos and flies.

The freshwater ecosystem includes lakes, ponds, rivers, and stream. Lakes are bodies of fresh water surronded by land, while ponds are smaller bodies of water.

Rivers and streams are moving bodies of freshwater. They usally originate in mountains and come from melting ground water and eventually flow into the ocean.

70% is from ice glaciers, ice caps , and as permanent snow.Every freshwater biome is unique because they all contain a range of animal and plant species, different climates, and various amounts of water. No two freshwater biomes are exactly the same.

These insects are very important in that they are a food source to many mammals, birds, and amphibians.

70% is from ice glaciers, ice caps , and as permanent snow.Every freshwater biome is unique because they all contain a range of animal and plant species, different climates, and various amounts of water. No two freshwater biomes are exactly the same.

These insects are very important in that they are a food source to many mammals, birds, and amphibians.

70% is from ice glaciers, ice caps , and as permanent snow.Every freshwater biome is unique because they all contain a range of animal and plant species, different climates, and various amounts of water. No two freshwater biomes are exactly the same.

These insects are very important in that they are a food source to many mammals, birds, and amphibians.

70% is from ice glaciers, ice caps , and as permanent snow.Every freshwater biome is unique because they all contain a range of animal and plant species, different climates, and various amounts of water. No two freshwater biomes are exactly the same.

These insects are very important in that they are a food source to many mammals, birds, and amphibians.

The freshwater biome compared to the other biomes **The blue is the freshwater biome**. The freshwater biome compared to the other biomes **The blue is the freshwater biome**.

A map of the freshwater in the 1989’s. A map of the freshwater in the 1989’s.

Cites: “Freshwater Biome Facts.” Freshwater Biome Facts. Web.

< "Facts About Freshwater Biomes." Facts About Freshwater Biomes. Web.

< How the Freshwater looks like. Cites: "Freshwater Biome Facts." Freshwater Biome Facts.

27 Apr. 2015.

27 Apr. 2015.

Cites: “Freshwater Biome Facts.” Freshwater Biome Facts. Web.

< "Facts About Freshwater Biomes." Facts About Freshwater Biomes. Web.

< How the Freshwater looks like. Cites: "Freshwater Biome Facts." Freshwater Biome Facts.

27 Apr. 2015.

27 Apr. 2015.

According to the USGS, the Earth contains about 332.5 million cubic miles (mi3), or 1,386 million cubic kilometers (km3) of water.

In geography, all the water on Earth, whether it is found in water bodies, the ground, the air, or in living organisms is known as the hydrosphere. The great majority of Earth’s water is contained in the oceans, seas, and bays with 96.5% and totals about 321,000,000 cubic miles.

Only about 2.5% of the Earth’s water is freshwater.

Outside of the polar regions, the world’s largest reservoir of freshwater is stored within tens of thousands of glaciers in the Tibetan Plateau. The Tibetan Plateau is nicknamed the “Third Pole” because of its enormous reservoir of freshwater.

The remaining 1.2% of the world’s freshwater is mainly from surface water such as lakes, ground ice cover, the atmosphere, and biological water.

The table below shows estimated sources of water. Source: Shiklomanov, 1993.

Read next: Groundwater on Earth. Shiklomanov, Igor.

“World fresh water resources”. Peter H.

The World’s Water. USGS.

1 WATER, WATER Everywhere But Not a Drop to Drink.

3 Where Does That Water Go.

4 Hydrologic Cycle. 5 Around and Around Water cycle Condensation Evaporation PrecipitationTranspiration Sun Clouds Runoff Groundwater Surface water Oceans, lakes, etc… Freshwater Saltwater.

7 Where is Water Found on Earth. Where It’s Found Oceans Lakes Rivers Ponds Streams Atmosphere Tissues and organs of living things Groundwater Surface Water States of Matter Liquid Frozen Gaseous Water Vapor.

The same amount of water that was here when Earth formed is still here. You might drink molecules that Neanderthals drank… Water is the only substance that is found naturally on earth in three forms: solid, liquid and gas Most of the Earth’s water is permanently frozen or salty.

Water regulates the earth’s temperature/climate. 9 97% covers the oceans % is frozen Of all the water on the Earth only 1% is available for us to drink.

11 Most (2%) of the freshwater on the Earth is locked up in iceMost (2%) of the freshwater on the Earth is locked up in ice. It’s found in Polar Ice Caps.

13 “Groundwater” “Glaciers” “Aquifers” “Wetlands”Freshwater Resources “Groundwater” “Glaciers” “Aquifers” “Wetlands”. 14 Where is Earth’s FRESHWATER.

If 1 L of water represents all of Earth’s water, a drop represents all the water in lakes and rivers.

16 Groundwater Water located below Earth’s Surface Largest Source of Freshwater in NORTH CAROLINA. 17 Glaciers-a mass of ice and snow that moves slowly over Earth’s Surface.

19 Are Icebergs\Glaciers Fresh or Salt Water.

Examples: Falls of the Neuse – Raleigh Little River Reservoir – Durham. 21 Aquifer (located underground) A rock layer that stores water and allows water to flow through it.

22 Water that seeps into the soil is groundwater Water that seeps into the soil is groundwater It travels through spaces between the rocks The type of rock determines how much water is stored and how fast it moves through the rocks Aquifers –store this freshwater underground Counties obtain drinking water and water for irrigation by tapping into aquifers.

24 Wetlands – Protected by Law and found “everywhere” on the Earth. 25 Wetlands Protected by Law.

27 Wetlands Act Like SpongesWetlands act as sponges in the landscape, collecting and holding rainwater to prevent flooding. Since they soak up pollutants and sediments they can improve the quality of the water that will eventually become drinking water for communities.

28 Wetland Facts 50% of the Earth’s “wetlands” have been lost since 1900Wetlands clean the rivers and lakes by removing pollution before the water enters the ocean They help stop floods by holding water from rain and melting snow. They act as a sponge.

ducks, shellfish and other small animals Provide home for many endangered species Every time a wetland is drained at least 500 hundred animals die because of lost of habitat and food. Many laws have been passed to save our wetlands.

30 Rivers of North Carolina. 31 Watershed – Drainage Basin River Basin – a drainage area of a riverWatershed – an area of land where rain collects and drains into a single place.

34 North Carolina’s “17” River Basins. 35 North Carolina’s “17” River Basins.

37 What Do You Think. Why do we need to protect the “Hydrosphere”.

What is the. 38 Environmental Protection AgencyResponsible for protecting and monitoring the Earth’s natural resources: Water Soil Air Plants Animals Minerals Rocks.

40 Notice how of the world’s total water supply of about 332Notice how of the world’s total water supply of about million cubic miles of water, over 96 percent is saline. And, of the total freshwater, over 68 percent is locked up in ice and glaciers.

Fresh surface-water sources, such as rivers and lakes, only constitute about 22,300 cubic miles (93,100 cubic kilometers), which is about percent of total water. Yet, rivers and lakes are the sources of most of the water people use everyday.

41 Salinity A measure of the amount of dissolved salts in a given amount of liquid (ocean water). 42 Water Conservation Americans use five times as much water as Europeans use.

43 Waste Disposal Groundwater Contamination. 44 3.

a) sedimentation c) filtration b) chlorination d) flotation. 45 Water Facts and Health A person can live about a month without food, but only a week without water.

Water removes waste from the human body. More than 2 billion people on earth do not have a safe supply of water.

A person must consume 2 liters of water daily to live healthily. You use an average of 168 gallons of water a day.

Water regulates the temperature of the human body. 46 Water is a Raw Material It takes 450 L (120 g) of water to produce one egg.

To process one can of fruit or vegetables we need 35 L (9.3 g) of water. About 25,700 L (6,800 g) of water is required to grow a day’s food for a family of four.

To manufacture new cars 148,000 L (39,000 g) of water are used per car. It takes 120 gallons of water to produce one egg.

47 Questions 1 1. Where is most freshwater located on Earth.

48 Answer 1. Where is most freshwater located on Earth.

49 Question 2 What are two sources of freshwater used by cities for drinking water. a.

Aquifers and reservoirs c. Wetlands and polar ice d.

50 Answer What are two sources of freshwater used by cities for drinking water. a.

Aquifers and reservoirs c. Wetlands and polar ice d.

51 Question 3 An area of land where precipitation moves from higher to lower elevations and then collects and drains into a stream or river is a tributary aquifer c. watershed d.

52 Answer An area of land where precipitation moves from higher to lower elevations and then collects and drains into a stream or river is a tributary aquifer c. watershed d.

Earth, our home, is the third planet from the sun. While scientists continue to hunt for clues of life beyond Earth, our home planet remains the only place in the universe where we’ve ever identified living organisms.

Earth is the fifth-largest planet in the solar system. It’s smaller than the four gas giants — Jupiter, Saturn, Uranus and Neptune — but larger than the three other rocky planets, Mercury, Mars and Venus.

But the spin of our home planet causes it to be squashed at its poles and swollen at the equator, making the true shape of the Earth an “oblate spheroid.”. Related: How big is Earth.

Our planet is unique for many reasons, but its available water and oxygen are two defining features. Water covers roughly 71% of Earth’s surface, with most of that water located in our planet’s oceans.

Related: 15 places on Earth that look exoplanetary. While Earth orbits the sun, the planet is simultaneously spinning around an imaginary line called an axis that runs through the core, from the North Pole to the South Pole.

Earth’s axis of rotation is tilted in relation to the ecliptic plane, an imaginary surface through the planet’s orbit around the sun. This means the Northern and Southern Hemispheres will sometimes point toward or away from the sun depending on the time of year, and this changes the amount of light the hemispheres receive, resulting in the changing seasons.

Earth’s orbit is not a perfect circle, but rather a slightly oval-shaped ellipse, similar to the orbits of all the other planets in our solar system. Our planet is a bit closer to the sun in early January and farther away in July, although this proximity has a much smaller effect on the temperatures we experience on the planet’s surface than does the tilt of Earth’s axis.

Statistics about Earth’s orbit, according to NASA:.

As the nebula collapsed under the force of its own gravity, it spun faster and flattened into a disk. Most of the material in that disk was then pulled toward the center to form the sun.

Scientists think Earth started off as a waterless mass of rock. “It was thought that because of these asteroids and comets flying around colliding with Earth, conditions on early Earth may have been hellish,” Simone Marchi, a planetary scientist at the Southwest Research Institute in Boulder, Colorado, previously told Space.com.

However, analyses of minerals trapped within ancient microscopic crystals suggest that there was liquid water already present on Earth during its first 500 million years, Marchi said. Radioactive materials in the rock and increasing pressure deep within the Earth generated enough heat to melt the planet’s interior, causing some chemicals to rise to the surface and form water, while others became the gases of the atmosphere.

Related: 10 Earth impact craters you must see.

Jack Wright, is an Internal Research Fellow with the European Space Agency (ESA).

Earth is also the only planet in the solar system with active plate tectonics, where the surface of the planet is divided into rigid plates that collide and move apart, causing earthquakes, mountain building, and volcanism. Sites of volcanism along Earth’s submarine plate boundaries are considered to be potential environments where life could have first emerged.

Earth is the right distance from the sun, such that liquid water has been stable in significant volumes over much of the planet’s lifetime. It has the right chemical ingredients for life (e.g.

Additional factors that have allowed the evolution of complex life are an oxygenated atmosphere, and protection from solar radiation by its magnetic field. New findings show that considering the average distance, Mercury is the nearest planet to Earth.

Mercury has no atmosphere and it has an old surface covered in impact craters, so it is very unlike Earth. One similarity is that Mercury and Earth both have internally generated magnetic fields.

There is emerging evidence for active volcanism on Venus, however, its atmosphere is up to 100 times denser than Earth’s and is mostly carbon dioxide with sulfuric acid clouds. The surface of Saturn’s moon Titan physically resembles Earth’s, with mountains, rivers, lakes, and seas.

Scientists estimated that 1 in 5 stars like our sun has one Earth-like planet orbiting around them, which may support life. Considering that there are more than 200 billion stars in our Milky Way, there might be an estimated 40 billion planets that might support life in our galaxy.

Earth observation from space provides objective coverage across both space and time. The same space-based sensor gathers data from sites across the world, including places too remote or otherwise inaccessible for ground-based data acquisition.

Looking back through archived satellite data shows us the steady clearing of the world’s rainforests, an apparent annual rise in sea level approaching 2 mm a year, and the increase of atmospheric pollution. In the long term, this monitoring of the Earth’s environment will enable a reliable assessment of the global impact of human activity and the likely future extent of climate change.

The consequences of a warming climate are far-reaching — affecting freshwater resources, global food production, and sea level and triggering an increase in extreme weather events. In order to tackle climate change, scientists and decision-makers need reliable data to understand how our planet is changing.

Earth is the only naturally habitable planet for complex (e.g. human) life in the solar system.

If Earth becomes uninhabitable we have nowhere else to go. Colonizing the Moon and Mars is no substitute for preserving Earth.

Earth’s core is about 4,400 miles (7,100 km) wide, slightly larger than half the Earth’s diameter and about the same size as Mars. The outermost 1,400 miles (2,250 km) of the core are liquid, while the inner core is solid.

The core is responsible for the planet’s magnetic field, which helps to deflect harmful charged particles shot from the sun.

The mantle is not completely stiff but can flow slowly. Earth’s crust floats on the mantle much as a piece of wood floats on water.

Related: Earth’s layers: Exploring our planet inside and out. Above the mantle, Earth has two kinds of crust.

Continental crust averages some 25 miles (40 km) thick, although it can be thinner or thicker in some areas. Oceanic crust is usually only about 5 miles (8 km) thick.

Earth gets warmer toward its core. At the bottom of the continental crust, temperatures reach about 1,800 degrees Fahrenheit (1,000 degrees Celsius), increasing about 3 degrees F per mile (1 degree C per km) below the crust.

Earth’s magnetic field is generated by currents flowing in Earth’s outer core. The magnetic poles are always on the move, with the magnetic North Pole accelerating its northward motion to 24 miles (40 km) annually.

Europa may have subsurface liquid water. Scientists hypothesize that Europa’s hidden ocean is salty, tidal, and causes its ice surface to move, resulting in large fractures that are clearly visible.

(Image Credit: NASA/JPL/Ted Stryk). Evidence points to oceans on other planets and moons, even within our own solar system.

In our solar system, Earth orbits around the sun in an area called the habitable zone. The temperature within this zone, along with an ample amount of atmospheric pressure, allow water to be liquid for long periods of time.

Saturn’s moon Enceladus and Jupiter’s moon Europa are two examples. Both appear to have salty, liquid oceans covered with thick layers of ice at the surface.

The existence of these geysers also tells scientists that these moons have a source of energy, perhaps from gravitational forces or radiation — energy that keeps the oceans liquid under the ice and could even support life.

Using mathematical models, researchers estimate that more than a quarter of known exoplanets may have liquid water, though the majority would have subsurface oceans like those on Europa and Enceladus. The search for liquid water is critical to the search for life beyond Earth.

Here on Earth, we have examples of life flourishing in some of the most extreme conditions, such as the complex ecosystems around hydrothermal vents on the seafloor. Scientists are reconsidering whether life could exist below an icy surface, even within our solar system on moons like Europa and Enceladus.

Are There Oceans on Other Worlds.

Europa Clipper Mission.

How to cite this article. Contact Us.

Ocean waters and waters trapped in the pore spaces of sediments make up most of the present-day hydrosphere. The total mass of water in the oceans equals about 50 percent of the mass of sedimentary rocks now in existence and about 5 percent of the mass of Earth’s crust as a whole.

The amount of water in the atmosphere at any one time is trivial, equivalent to roughly 13,000 cubic km (about 3,100 cubic miles) of liquid water, or about 0.001 percent of the total at Earth’s surface. This water, however, plays an important role in the water cycle.

Although water storage in rivers, lakes, and the atmosphere is small, the rate of water circulation through the rain-river-ocean-atmosphere system is relatively rapid. The amount of water discharged each year into the oceans from the land is approximately equal to the total mass of water stored at any instant in rivers and lakes.

It is this small amount of water, however, that exerts the most direct influence on evaporation from soils. The biosphere, though primarily H2O in composition, contains very little of the total water at the terrestrial surface, only about 0.00004 percent, yet the biosphere plays a major role in the transport of water vapour back into the atmosphere by the process of transpiration.

Thus, the masses of water at Earth’s surface are major receptacles of inorganic and organic substances, and water movement plays a dominant role in the transportation of these substances about the planet’s surface.

Earth’s inner core is the innermost geologic layer of the planet Earth. It is primarily a solid ball with a radius of about 1,220 km (760 mi), which is about 20% of Earth radius or 70% of the Moon’s radius.

There are no samples of Earth’s core accessible for direct measurement, as there are for Earth’s mantle. Information about Earth’s core mostly comes from analysis of seismic waves and Earth’s magnetic field.

The temperature at the inner core’s surface is estimated to be approximately 5,700 K (5,430 °C. 9,800 °F), which is about the temperature at the surface of the Sun.

Earth was discovered to have a solid inner core distinct from its molten outer core in 1936, by the Danish seismologist Inge Lehmann, who deduced its presence by studying seismograms from earthquakes in New Zealand. She observed that the seismic waves reflect off the boundary of the inner core and can be detected by sensitive seismographs on the Earth’s surface.

In 1938, Beno Gutenberg and Charles Richter analyzed a more extensive set of data and estimated the thickness of the outer core as 1,950 km (1,210 mi) with a steep but continuous 300 km (190 mi) thick transition to the inner core. implying a radius between 1,230 and 1,530 km (760 and 950 mi) for the inner core.

A few years later, in 1940, it was hypothesized that this inner core was made of solid iron. In 1952, Francis Birch published a detailed analysis of the available data and concluded that the inner core was probably crystalline iron.

The boundary between the inner and outer cores is sometimes called the “Lehmann discontinuity”, although the name usually refers to another discontinuity. The name “Bullen” or “Lehmann-Bullen discontinuity”, after Keith Edward Bullen has been proposed, but its use seems to be rare.

Adam Dziewonski and James Freeman Gilbert established that measurements of normal modes of vibration of Earth caused by large earthquakes were consistent with a liquid outer core. In 2005, shear waves were detected passing through the inner core.

Almost all direct measurements that scientists have about the physical properties of the inner core are the seismic waves that pass through it. Deep earthquakes generate the most informative waves, 30 km or more below the surface of the Earth (where the mantle is relatively more homogeneous) and are recorded by seismographs as they reach the surface, all over the globe.[citation needed].

The two waves have different velocities and are damped at different rates as they travel through the same material.

Also of interest are the “PKIKP” waves, that travel through the inner core (I) instead of being reflected at its surface (i). Those signals are easier to interpret when the path from source to detector is close to a straight line—namely, when the receiver is just above the source for the reflected PKiKP waves, and antipodal to it for the transmitted PKIKP waves.

While S waves cannot reach or leave the inner core as such, P waves can be converted into S waves, and vice versa, as they hit the boundary between the inner and outer core at an oblique angle. The “PKJKP” waves are similar to the PKIKP waves, but are converted into S waves when they enter the inner core, travel through it as S waves (J), and are converted again into P waves when they exit the inner core.

Other sources of information about the inner core include. The velocity of the S waves in the core varies smoothly from about 3.7 km/s at the center to about 3.5 km/s at the surface.

: fig.2. The velocity of the P-waves in the core also varies smoothly through the inner core, from about 11.4 km/s at the center to about 11.1 km/s at the surface.

: fig.2. On the basis of the seismic data, the inner core is estimated to be about 1221 km in radius (2442 km in diameter), which is about 19% of the radius of the Earth and 70% of the radius of the Moon.

Its volume is about 7.6 billion cubic km (7.6 × 1018 m3), which is about 1⁄146 (0.69%) of the volume of the whole Earth.

In comparison, the flattening of the Earth as a whole is close to 1⁄300, and the polar radius is 21 km shorter than the equatorial one.

The acceleration of gravity at the surface of the inner core can be computed to be 4.3 m/s2. which is less than half the value at the surface of the Earth (9.8 m/s2).

The density of the inner core is believed to vary smoothly from about 13.0 kg/L (= g/cm3 = t/m3) at the center to about 12.8 kg/L at the surface. As it happens with other material properties, the density drops suddenly at that surface: The liquid just above the inner core is believed to be significantly less dense, at about 12.1 kg/L.

That density implies a mass of about 1023 kg for the inner core, which is 1⁄60 (1.7%) of the mass of the whole Earth.

From these considerations, in 2002, D. Alfè and others estimated its temperature as between 5,400 K (5,100 °C.

9,800 °F). However, in 2013, S.

10,754 ± 900 °F).

In 2010, Bruce Buffett determined that the average magnetic field in the liquid outer core is about 2.5 milliteslas (25 gauss), which is about 40 times the maximum strength at the surface. He started from the known fact that the Moon and Sun cause tides in the liquid outer core, just as they do on the oceans on the surface.

This dissipation, in turn, damps the tidal motions and explains previously detected anomalies in Earth’s nutation. From the magnitude of the latter effect he could calculate the magnetic field.

While indirect, this measurement does not depend significantly on any assumptions about the evolution of the Earth or the composition of the core.

Some scientists have therefore considered whether there may be slow convection in the inner core (as is believed to exist in the mantle). That could be an explanation for the anisotropy detected in seismic studies.

Buffett estimated the viscosity of the inner core at 1018 Pa·s, which is a sextillion times the viscosity of water, and more than a billion times that of pitch.

However, based on the relative prevalence of various chemical elements in the Solar System, the theory of planetary formation, and constraints imposed or implied by the chemistry of the rest of the Earth’s volume, the inner core is believed to consist primarily of an iron–nickel alloy.

That result implies the presence of lighter elements in the core, such as silicon, oxygen, or sulfur, in addition to the probable presence of nickel. Recent estimates (2007) allow for up to 10% nickel and 2–3% of unidentified lighter elements.

According to computations by D. Alfè and others, the liquid outer core contains 8–13% of oxygen, but as the iron crystallizes out to form the inner core the oxygen is mostly left in the liquid.

Groundwater is the water present beneath Earth’s surface in rock and soil pore spaces and in the fractures of rock formations. About 30 percent of all readily available freshwater in the world is groundwater.

The depth at which soil pore spaces or fractures and voids in rock become completely saturated with water is called the water table. Groundwater is recharged from the surface.

Groundwater is also often withdrawn for agricultural, municipal, and industrial use by constructing and operating extraction wells. The study of the distribution and movement of groundwater is hydrogeology, also called groundwater hydrology.

Typically, groundwater is thought of as water flowing through shallow aquifers, but, in the technical sense, it can also contain soil moisture, permafrost (frozen soil), immobile water in very low permeability bedrock, and deep geothermal or oil formation water. Groundwater is hypothesized to provide lubrication that can possibly influence the movement of faults.

Groundwater is often cheaper, more convenient and less vulnerable to pollution than surface water. Therefore, it is commonly used for public water supplies.

Underground reservoirs contain far more water than the capacity of all surface reservoirs and lakes in the US, including the Great Lakes. Many municipal water supplies are derived solely from groundwater.

Human use of groundwater causes environmental problems. For example, polluted groundwater is less visible and more difficult to clean up than pollution in rivers and lakes.

Major sources include industrial and household chemicals and garbage landfills, excessive fertilizers and pesticides used in agriculture, industrial waste lagoons, tailings and process wastewater from mines, industrial fracking, oil field brine pits, leaking underground oil storage tanks and pipelines, sewage sludge and septic systems.

These issues are made more complicated by sea level rise and other effects of climate change, particularly those on the water cycle. Earth’s axial tilt has shifted 31 inches because of human groundwater pumping.

Groundwater is fresh water located in the subsurface pore space of soil and rocks. It is also water that is flowing within aquifers below the water table.

Groundwater can be thought of in the same terms as surface water: inputs, outputs and storage. The natural input to groundwater is seepage from surface water.

Due to its slow rate of turnover, groundwater storage is generally much larger (in volume) compared to inputs than it is for surface water. This difference makes it easy for humans to use groundwater unsustainable for a long time without severe consequences.

Groundwater is naturally replenished by surface water from precipitation, streams, and rivers when this recharge reaches the water table.

Deep groundwater (which is quite distant from the surface recharge) can take a very long time to complete its natural cycle.

By analysing the trace elements in water sourced from deep underground, hydrogeologists have been able to determine that water extracted from these aquifers can be more than 1 million years old.

Where water recharges the aquifers along the Eastern Divide, ages are young. As groundwater flows westward across the continent, it increases in age, with the oldest groundwater occurring in the western parts.

Groundwater recharge or deep drainage or deep percolation is a hydrologic process, where water moves downward from surface water to groundwater. Recharge is the primary method through which water enters an aquifer.

Groundwater recharge also encompasses water moving away from the water table farther into the saturated zone. Recharge occurs both naturally (through the water cycle) and through anthropogenic processes (i.e., “artificial groundwater recharge”), where rainwater and or reclaimed water is routed to the subsurface.

The high specific heat capacity of water and the insulating effect of soil and rock can mitigate the effects of climate and maintain groundwater at a relatively steady temperature. In some places where groundwater temperatures are maintained by this effect at about 10 °C (50 °F), groundwater can be used for controlling the temperature inside structures at the surface.

During cold seasons, because it is relatively warm, the water can be used in the same way as a source of heat for heat pumps that is much more efficient than using air.

About 99% of the world’s liquid fresh water is groundwater. Global groundwater storage is roughly equal to the total amount of freshwater stored in the snow and ice pack, including the north and south poles.

The volume of groundwater in an aquifer can be estimated by measuring water levels in local wells and by examining geologic records from well-drilling to determine the extent, depth and thickness of water-bearing sediments and rocks. Before an investment is made in production wells, test wells may be drilled to measure the depths at which water is encountered and collect samples of soils, rock and water for laboratory analyses.

The characteristics of aquifers vary with the geology and structure of the substrate and topography in which they occur. In general, the more productive aquifers occur in sedimentary geologic formations.

Unconsolidated to poorly cemented alluvial materials that have accumulated as valley-filling sediments in major river valleys and geologically subsiding structural basins are included among the most productive sources of groundwater.

the mechanisms by which this occurs are the subject of fault zone hydrogeology.

Groundwater is the most accessed source of freshwater around the world, including as drinking water, irrigation, and manufacturing. Groundwater accounts for about half of the world’s drinking water, 40% of its irrigation water, and a third of water for industrial purposes.

Another estimate stated that globally groundwater accounts for about one third of all water withdrawals, and surface water for the other two thirds. : 21 Groundwater provides drinking water to at least 50% of the global population.

A similar estimate was published in 2021 which stated that “groundwater is estimated to supply between a quarter and a third of the world’s annual freshwater withdrawals to meet agricultural, industrial and domestic demands.” : 1091. Global freshwater withdrawal was probably around 600 km³ per year in 1900 and increased to 3,880 km³ per year in 2017.