What Is the Hydrosphere?
There are many kinds and forms of water all over the planet. Water appears in liquid form as rain, and forming lakes, oceans, rivers and seas. Water appears as a gas in the form of water vapor and exists as a solid in the form of ice and snow.
Water on Earth
Oceans and seas contain most of the world’s water. Since this water contains salt, it’s unsuitable for human consumption and for agriculture. Although oceans and therefore water cover 71% of the Earth’s surface, humans have only explored as little as 5% of it.
Freshwater in Lakes
Freshwater, the water humans require for agriculture and to drink can be found in large bodies of water called lakes. Lakes and other freshwater bodies cover about 20% of Earth’s surface.
Freshwater in Rivers
Rivers are freshwater channels running over land. Rivers flow towards an ocean, sea, lake, or another river. Water from rivers is used by humans for both consumption and agricultural use.
Water in the Sky
Water can also be found in clouds as condensed water vapor. Water falling from clouds is called precipitation. Types of precipitation includes snow, rain, or a combination of both called sleet.
Amount of Freshwater
97% of Earth’s water is found in oceans and seas. The remaining 3% is freshwater, however most of it is “locked up” in the polar ice caps, glaciers, and permafrost. Of all the world’s water, humans can only access 0.007% for consumption and agriculture.
Clouds and Precipitation
Water vapor is continually cycling around Earth via processes called evaporation and precipitation. These processes are part of a larger system called a water cycle. The process of evaporation is involved in the creation of clouds and the term precipitation refers to water that falls from the clouds.
Heat from the sun excites the tightly clustered water molecules, which start to drift apart. When this occurs, the water becomes a gas called water vapor, which rises into the sky, leaving the clothes dry. This process is called evaporation.
When the water vapor rises, it starts to cool down, which encourages the water molecules to get closer together. As more water vapor arrives via wind and evaporation, a cloud starts to form.
Once a cloud is formed, if the water vapor continues to condense (get closer together), water droplets begin to form. Once these water droplets are too heavy to remain in the air, they fall as rain or hail.
Snow is formed when the water vapor becomes frozen and turns into tiny ice crystals. As these ice crystals condense, they join up with other ice crystals before becoming too heavy to remain in the air.
Oceans and Seas
Oceans and seas are huge bodies of salt water that cover 71% of the Earth’s surface. A sea is a body of salt water that is bordered by land while oceans are wide expanses of salt water. Seas and oceans vary in depth.
The depth of the water determines how much sunlight can travel through, which in turn determines the species of plants and animals that live there.
The zone where the sea meets the land is called the coast. Coasts around the world measure about 193,000 miles. Coastal areas can also be called shores and seasides.
The sea gets deeper as it follows the continental shelf. The continental shelf is the area of land found below sea level that is part of the larger land mass. This part of the sea can contain coral reefs in warmer climates.
Between the continental shelf and the ocean floor lies an area called the continental slope. Animals such as deep sea fish, crabs, and whales can be found living in these areas.
No sunlight reaches this area and animals living here need to have evolved special adaptations, with some species even producing their own light (called bioluminescence). The deepest known point of the ocean is in the Mariana Trench, measured at 36,070 feet.
Lakes are large areas of freshwater surrounded by land. Many lakes in the Northern Hemisphere were formed by glacial activities, whereas lakes found in the Southern Hemisphere are more commonly created by land depression.
Water that is surrounded by land but also connected to the sea is called a lagoon.
Lakes are stand–alone bodies of water, not directly connected to the sea (otherwise they would be called lagoons). In most cases, lakes are fed and drained by rivers or streams.
Some lakes were formed by water falling into low-lying areas and pooling. Other lakes were created after big, moving rivers of ice called glaciers pushed along land and changed the Earth, making deep bowls where lakes formed when the glaciers melted.
Lake Baikal in Russia, the deepest lake in the world, is 5,354 feet deep at its deepest point. It’s known as the largest lake in the world because it holds the most water. This ancient lake is estimated to be 25–30 million years old.
Rivers and Underground Water
A river is a body of water that flows. Rather than sitting mostly in one place like lakes and ponds, rivers move in one direction. Most rivers begin in a higher area such as a mountain and end up flowing into a sea.
The place where the river begins is called its source. The source may be a melting glacier, a spring, or a lake. Rain, snowfall, and groundwater also help a river to form.
As the river travels over flatter areas, it curves like an “s.” These curves are called meanders. As the river travels, it cuts through the Earth, making new shapes and pushing deep into the rock. Some rivers also fall over rocks and cliffs, making waterfalls.
All rivers empty into larger bodies of waters. Many rivers reach the ocean while others flow into seas or large lakes. The area where the river ends is called the river’s mouth.
30% of the Earth’s freshwater is located underground. Groundwater is stored in the spaces between soil and rock. When groundwater is collected in one area it is called an aquifer. In some areas the groundwater appears on the Earth’s surface.
Groundwater is stored in the spaces between soil and rock in something called aquifers. Aquifers are like reservoirs, only they are located underground. Wells are built to reach an aquifer.
In some areas the groundwater appears on the Earth’s surface. This is called a spring. Hot springs occur when the groundwater has been in contact with molten rock from under the Earth.
Grand Prismatic Spring, Wyoming
Grand Prismatic Spring in the United States is a type of hot spring. It is famous for its multi-hued appearance, which is caused by the bacteria living within it. A different type of cyanobacteria produces each colored band.
Humans and the Hydrosphere
All animals and plants need the hydrosphere to stay alive. In order for humans to survive, we need to look after the 0.007% of freshwater available to use.
Stricter environmental regulations for industry and agriculture can ensure freshwater supplies remain suitable for human and other species use.
Before stricter environmental laws, factories disposed of much of their waste into river systems. This type of water pollution can quickly cause a river to become unsuitable for human use.
Modern day agricultural practices can affect life in rivers, lakes, and oceans. When farmers put chemicals on their fields to get rid of weeds and insects, the rain water washes the chemicals into rivers. Contaminated water can also seep into groundwater.
When oil spills occur, oil floats on top of the water, forming a barrier that prevents sunlight and oxygen from getting through. Phytoplankton die (the basis of many food chains), animals suffocate, and animals coated by oil can’t regulate their body temperatures to keep warm.