My Science School

A stream or river that flows into a larger river, rather than directly to the sea, is called a tributary. Some large rivers have hundreds of tributaries!

The larger, or parent, river is called the mainstem. The point where a tributary meets the mainstem is called the confluence. Tributaries, also called affluents, do not flow directly into the ocean.

Most large rivers are formed from many tributaries. Each tributary drains a different watershed, carrying runoff and snow melt from that area. Each tributary's watershed makes up the larger watershed of the mainstem. 

Sometimes, tributaries have the same name as the river into which they drain. These tributaries are called forks. Different forks are usually identified by the direction in which they flow into the mainstem.

The opposite of a tributary is a distributary. A distributary is a stream that branches off and flows apart from the mainstem of a stream or river. The process is called river bifurcation. 

 

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When sea water filters down cracks in the Earth’s crust, it is heated by volcanic activity. Hot water then spurts out through the cracks or vents.

Hydrothermal vents exist because the earth is both geologically active and has large amounts of water on its surface and within its crust. Under the sea, hydrothermal vents may form features called black smokers or white smokers. Relative to the majority of the deep sea, the areas around submarine hydrothermal vents are biologically more productive, often hosting complex communities fueled by the chemicals dissolved in the vent fluids. Chemosynthetic bacteria and archaea form the base of the food chain, supporting diverse organisms, including giant tube worms, clams, limpets and shrimp. Active hydrothermal vents are believed to exist on Jupiter's moon Europa, and Saturn's moon Enceladus, and it is speculated that ancient hydrothermal vents once existed on Mars.

Hydrothermal vents in the deep ocean typically form along the mid-ocean ridges, such as the East Pacific Rise and the Mid-Atlantic Ridge. These are locations where two tectonic plates are diverging and new crust is being formed.

The water that issues from seafloor hydrothermal vents consists mostly of sea water drawn into the hydrothermal system close to the volcanic edifice through faults and porous sediments or volcanic strata, plus some magmatic water released by the upwelling magma. In terrestrial hydrothermal systems, the majority of water circulated within the fumarole and geyser systems is meteoric water plus ground water that has percolated down into the thermal system from the surface, but it also commonly contains some portion of metamorphic water, magmatic water, and sedimentary formational brine that is released by the magma. The proportion of each varies from location to location.

 

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A mid-ocean ridge or mid-oceanic ridge is an underwater mountain range, formed by plate tectonics.

This uplifting of the ocean floor occurs when convection currents rise in the mantle beneath the oceanic crust and create magma where two tectonic plates meet at a divergent boundary.

The mid-ocean ridges of the world are connected and form a single global mid-oceanic ridge system that is part of every ocean, making the mid-oceanic ridge system the longest mountain range in the world, with a total length of about 60,000 km.

There are two processes, ridge-push and slab-pull, thought to be responsible for the spreading seen at mid-ocean ridges, and there is some uncertainty as to which is dominant.

Ridge-push occurs when the weight of the ridge pushes the rest of the tectonic plate away from the ridge, often towards a subduction zone.

At the subduction zone, "slab-pull" comes into effect.

This is simply the weight of the tectonic plate being subducted (pulled) below the overlying plate dragging the rest of the plate along behind it.

The other process proposed to contribute to the formation of new oceanic crust at mid-ocean ridges is the "mantle conveyor".

 

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When the tide goes out on rocky seashore, pools of water are left behind in holes in the rocks. These then become home to a huge range of plants and animals, such as shellfish and sea anemones.

As the tide recedes, not the entire coast is left behind dry. Depending on the type of rock, one can find shallow or deep rock pools. They offer better survival chances for animals and plants that need to be submerged all the time. Because each rock pool is different, they invite different communities. Deep rock pools near the low tide, have few survival problems, whereas shallow rock pools near the high tide, have many. Thus the pool's placing on the shore as well as its depth and size are important factors.

Deep rock pools provide shelter from waves, allowing fragile organisms to live on an otherwise exposed rocky shore. Fragile animals are: sea slugs, shrimps, camouflage crabs, sea eggs, and small fishes. Fragile sea weeds are: Neptune’s necklace, pillow weed, cystophora, sea lettuce and many others.

For the snails that are able to survive in between high and low tide (periwinkle, nerita, melagraphia, cats eye) a rock pool is not necessarily a better place because their predators are found there (dark rock shell, white rock shell, trumpet shell). Large fish and octopus may find the rock pools too small, lacking oxygen for breathing. Rock pools may collect fresh water during rain storms, which is worse for shallow rock pools high up the shore where organisms must wait longer for the tide to return.

 

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These are made from the skeletons left by tiny sea animals, called coral polyps, when they die. The skeletons build up into huge reefs, where plants and other sea creatures live. The coral species that build reefs are known as hermatypic, or "hard," corals because they extract calcium carbonate from seawater to create a hard, durable exoskeleton that protects their soft, sac-like bodies. Other species of corals that are not involved in reef building are known as “soft” corals.

Each individual coral is referred to as a polyp. Coral polyps live on the calcium carbonate exoskeletons of their ancestors, adding their own exoskeleton to the existing coral structure. As the centuries pass, the coral reef gradually grows one tiny exoskeleton at a time, until they become massive features of the marine environment.

Corals are found all over the world's oceans, from the Aleutian Islands off the coast of Alaska to the warm tropical waters of the Caribbean Sea. The biggest coral reefs are found in the clear, shallow waters of the tropics and subtropics. The largest of these coral reef systems, the Great Barrier Reef in Australia, is more than 1,500 miles long (2,400 kilometers).

 

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When tectonic plates in the ocean floor move and collide, one may be pushed under the other, creating a narrow trench. These trenches are the deepest places in the Earth’s oceans.

Trenches are formed by subduction, a geophysical process in which two or more of Earth's tectonic plates converge and the older, denser plate is pushed beneath the lighter plate and deep into the mantle, causing the seafloor and outermost crust (the lithosphere) to bend and form a steep, V-shaped depression. This process makes trenches dynamic geological features—they account for a significant part of Earth’s seismic activity—and are frequently the site of large earthquakes, including some of the largest earthquakes on record. Subduction also generates an upwelling of molten crust that forms mountain ridges and volcanic islands parallel to the trench. Examples of these volcanic "arcs" can be seen in the Japanese Archipelago, the Aleutian Islands, and many other locations around this area called the Pacific "Ring of Fire."

Many of the organisms living in trenches have evolved surprising ways to survive in these unique environments. Recent discoveries in the hadal zone have revealed organisms with proteins and biomolecules suited to resisting the crushing hydrostatic pressure and others able to harness energy from the chemicals that leak out of hydrocarbon seeps and mud volcanoes on the seafloor. Other hadal species thrive on the organic material that that drifts down from the sea surface and is funneled to the axis of the V-shaped trenches.

 

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This is the top layer of the ocean, nearest the surface. The open ocean is vast. Although food can sometimes be hard to find, many animals, such as dolphins, seals, and turtles, live there.

Many open ocean organisms live out their existence without ever coming into contact with the shore, the seafloor, or the water’s surface. They spend their entire lives surrounded by water on all sides and do not know that anything else even exists. In the case of the deep open ocean, organisms never even see sunlight. As land mammals that breathe air, walk on land, and rely on our sense of sight for almost all functions, it is difficult for people (even experts) to comprehend that most of the organisms on the planet are never exposed to air, land, or sunlight.

 

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These islands are formed from layers of magma, or liquid rock, which erupts from a volcano under the water, then cools and hardens. The magma layers eventually build up to create an island.

Volcanic islands are formed by volcanic activity on the seabed, often near the boundaries of the tectonic plates that form Earth’s crust. Where two plates pull apart, lava erupts to form an undersea ridge. Layers of lava build up until a ridge breaks the sea’s surface to form an island. Sometimes a whole chain of volcanic islands, called an island arc, is formed in this way. Some island arcs contain thousands of islands.

Sometimes, volcanoes occur in close proximity to each other on the sea floor, creating a very large island. For example, the big island of Hawaii is actually five, side-by-side volcanoes that have grown together. The island chain of countries that make up Southeast Asia; Indonesia and Papua New Guinea, the Philippine Islands were all created by volcanic activity on the sea floor. New Zealand, the Island country off the Southeast coast of Australia, was also formed by ancient volcanoes.

 

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Around 71 percent of the Earth’s surface is covered by oceans. Many different and interesting features are found in and around them, and a huge variety of animals and plants have adapted to life in this watery world. Humans depend on these teeming waters for comfort and survival, but global warming and overfishing threaten to leave the ocean agitated and empty.

The oceans hold about 320 million cubic miles (1.35 billion cubic kilometers) of water, which is roughly 97 percent of Earth's water supply. The water is about 3.5 percent salts and contains traces of all chemical elements found on Earth. The oceans absorb the sun's heat, transferring it to the atmosphere and distributing it around the world via the ever-moving ocean currents. This drives global weather patterns and acts as a heater in the winter and an air conditioner in the summer.

 

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We use large quantities of water. We drink it, wash with it, use it in industry, and also prepare food with it. Below are the percentage of the water that each person uses every day for these activities.

Drinking:

Only a 0.2% of the water a person uses every day is for drinking. Your drinking water comes from natural sources that are either groundwater or surface water.

Groundwater comes from rain and snow that seeps into the ground. The water gets stored in open spaces and pores or in layers of sand and gravel known as aquifers. We use water wells or springs to harvest this groundwater.

Surface Water also comes from rain and snow. It is the water that fills the rivers, lakes, and streams.

Personal:

Nearly 4.2% of the water a person uses for washing, cleaning your teeth, and flushing the toilet use up this share. Water generally gets to our homes in one of two ways. Either it is delivered by a city/county water department (or maybe from a private company), or people supply their own water, normally from a well. Water delivered to homes is called "public-supplied deliveries" and water that people supply themselves is called "self supplied", and is almost always from groundwater.

Manufactured goods:

Nearly 30.6% of water a person use for manufactured goods. The industries that produce metals, wood and paper products, chemicals, gasoline and oils, and those invaluable grabber utensils you use to get your ring out of the garbage disposal are major users of water. Probably every manufactured product uses water during some part of the production process. Industrial water use includes water used for such purposes as fabricating, processing, washing, diluting, cooling, or transporting a product; incorporating water into a product; or for sanitation needs within the manufacturing facility. Some industries that use large amounts of water produce such commodities as food, paper, chemicals, refined petroleum, or primary metals.

Food production:

This takes up most of the water we use. Water is an essential part of our diet. Without it, our bodies would not work! For vegetative growth and development plants require water in adequate quantity and at the right time. Crops have very specific water requirements, and these vary depending on local climate conditions. The production of meat requires between six and twenty time more water than for cereals. 

 

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Earth’s water is always moving from one place to another. This process, called the water cycle, is a continuous journey, in which water moves between the land, the atmosphere, and the ocean.

The water cycle shows the continuous movement of water within the Earth and atmosphere. It is a complex system that includes many different processes. Liquid water evaporates into water vapor, condenses to form clouds, and precipitates back to earth in the form of rain and snow. Water in different phases moves through the atmosphere (transportation). Liquid water flows across land (runoff), into the ground (infiltration and percolation), and through the ground (groundwater). Groundwater moves into plants (plant uptake) and evaporates from plants into the atmosphere (transpiration). Solid ice and snow can turn directly into gas (sublimation). The opposite can also take place when water vapor becomes solid (deposition). 

 

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Most of the water on Earth is in the ocean – in fact, nearly 97%. The remaining 3% is freshwater and is stored in ice sheets, ice caps and glaciers, groundwater, and surface water such as lakes and rivers. The majority of this freshwater is frozen and stored in the Antarctic and Greenland ice sheets. Glaciers around the world are changing rapidly. In general, freezing and melting are a natural part of the water cycle, but for glaciers, more ice is melting each summer than falls as snow during the winter, and they are shrinking in size as a result. Glaciers also provide water resources, like drinking water, for downstream communities, but as the size of these glaciers changes, so too does this important resource.

 

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Water is essential to life on Earth. Without it, plants and animals would not be able to survive. Around 71 per cent of Earth is covered in water in water. This includes both salt water and fresh water. Not all of Earth’s water is easily available for us to use.

The water is concentrated at the Earth’s surface, so its relative mass compared to the whole Earth is small. It amounts to about 0.02 % of Earth’s mass!

The largest drop here represents the volume of all water, the mid sized drop freshwater, and the smallest drop (near Atlanta) all of Earth’s lake water.

 

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Over thousands of years, many different natural features, or landforms, have developed in deserts. A desert landform is a place that gets little to no rain. The climate can be either hot or cold and sometimes both. Each desert landform has one thing in common; it has less than 10 inches of rain per year. Usually deserts have a lot of wind because they are flat and have no vegetation to block out the wind.These include hills; mountains; narrow, steep-sided valleys called canyons; large, flat areas called plains; sand dunes; strange rock formations; and oases.

1. Sand dunes: These hills are formed by the wind blowing across the desert sand, so that it piles up. The most common in deserts include barchans and seif dunes. Barchan dunes are formed due to the wind action resulting in crescent-shaped dunes. These small crescent-shaped sand bodies form in locations where the wind blows consistently from one direction. Seif dunes, on the other hand, are long and narrow with a sharp crest common in the Sahara. They can also form a long chain of dunes.

2. Oases: Rare underground water can create pools of water. Plants then spring up around them. Oases typically occurs in the middle of a desert. They are fertile areas of the desert consisting of one or multiple springs surrounded by vegetation. Oasis is formed due to a mix of extreme temperatures resulting in islands of life. This comes about because the oases is situated in parts of the desert where the elevation is so low that the water table is just near the surface enabling vegetation to flourish.

3. Mesas and buttes: A mesa is a hill with steep sides and a flat top. A smaller mesa is sometimes called a butte. These landforms can also be called table mountains or table hills, because the word mesa actually means table in Spanish.

Scientists believe that mesas and buttes were formed when streams or rivers weathered and eroded away the smaller, softer rocks, leaving only the strong rock of the mesa or butte behind.

 

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These are extremely dry and cold. Temperatures rarely rise above 10° C (50° F), even in summer. Some are covered in ice and snow all year, while others are covered in gravel and large rocks. Most of Antarctica is polar desert.

Ross Island is located in Ross Sea, Antarctica and in McMurdo Sound. Due to the persistent presence of ice sheet, the isle is sometimes taken to be part of mainland Antarctica. The island is 43 miles (69 km) long and 45 miles wide. On it are Mount Erebus (an active volcano 12,450 feet [3,800 metres] high) and Mount Terror (10,750 feet) among a series of mountain ranges intersected by deep valleys. Mount Erebus was the site in 1979 of a crash that claimed 257 lives on a sightseeing and photographic flight over Antarctica. The ranges are free of snow except for hanging glaciers on the highest slopes. McMurdo, a U.S. base, is located on the island just north of Cape Armitage, its southernmost extremity. About one mile south is Scott Base, a New Zealand station. A steep pyramid of rock called Observation Hill rises between the two stations. In 1907 Ernest Shackleton, a British explorer, established a camp at Camp Royds, and Robert Falcon Scott, in 1910, set up a camp at Cape Evans on his return expedition. These are now maintained as historic monuments.

 

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