The Hydrosphere is a combination of mass of water and the Earth's hydrosphere is made of oceans, lakes and rivers, glaciers, ice caps and icebergs. The composition of the hydrosphere in terms of percentage of water are Oceans (97.6), Saline lakes and inland seas (0.008), Ice caps and glaciers (1.9), Ground water (0.5), Soil moisture (0.01), Lakes (0.009) Fresh water rivers (0.0001), Atmosphere (0.0009). Here, we are giving interesting facts about Earth’s Hydrosphere for enhancing the knowledge of aspirant who are preparing for different competitive exams.
1. Pacific Ocean is the deepest ocean and the world's deepest trench i.e., Mariana trench lies in the Pacific Ocean. The longest coastlines are associated with Atlantic Ocean. Pacific Ocean is nearly circular, but Atlantic Ocean is 'S' shaped.
2. Indian Ocean is the only ocean named after a country. It is deeper than the Atlantic Ocean. Here, the number of Continental Island is more than that of volcanic island. Arctic Ocean is the smallest ocean and lies within the Arctic Circle. The North Pole lies in the middle of the Arctic Ocean.
3. The Submarine relief features are classified from coast to Deep Ocean, as: continental shelf, continental slope, continental rise, and deep sea plain / abyssal plain and ocean deeps.
4. Continental shelf marks the sea ward limit of the continental block. It is shallow seaward extension of continents having depth up-to 200 m and slope is very smooth. Due to penetration of sunlight, planktons grow abundantly acting as food for fishes. So, continental shelves are major fishing grounds of the world. At the edge of the continental shelf, there is an abrupt change of gradient, to about 1 in 20, forming the continental slope. The submarine canyons are formed by turbidity currents in the continental slopes.
5. Continental rises are the falling slopes in the oceans where slope is very stiff and no such deposition is found, these are of tectonic origin, trenches are found near its foot limit as sub-duction zones.
6. The deep sea plains are the undulating plains lying 2 to 3 miles below sea level and covers about 76% of ocean floor, generally termed as abyssal plain. These have extensive submarine plateaus, ridges, trenches, oceanic islands etc. Deep sea is mostly characterised by the pelagic deposits of plants, marine animals and plants. It is devoid of erosion deposits. Atlantic Ocean has comparatives lower extent of deep sea plains due to larger extent of continental shelves.
7. Ocean deeps represent the depressions and trenches on the ocean floors. They are the deepest zones of the ocean basin. They are generally located parallel to the coasts facing mountains and along the islands. Mariana trench, Mindanao trench etc are examples of ocean deeps.
8. Mid oceanic ridges are the continuous series of mountain chains found in the abyssal plains and are of volcanic/tectonic origin. It marks the constructive plate boundary where two plates separate from each other and magma erupts and mountains are formed. It is most continuous in Atlantic Ocean and found in every ocean.
9. Ocean deposits are mainly of three types: the Mud’s or terrigenous derived from land and deposited on the continental shelves, the oozes or pelagic deposits derived from Shelly and skeletal remains of marine micro organism with calcareous or siliceous parts and the clays occurs mainly as red clays in the deeper part of the ocean basins believed to be accumulation of volcanic dusts.
10. Salinity is the degree of saltiness of water, either as percentage or more often in parts per thousand (%0) and salts of the oceans is mainly of sodium chloride and magnesium chloride. Isohaline is the line joining places having equal degree of salinity. Lake Van has highest salinity and open seas are of less salinity than closed seas.
11. Ocean temperature is mainly distributed through warm and cold ocean currents. The highest water temperature is found in enclosed seas on the tropics. Temperature of the oceans also varies vertically with increasing depth.
12. Temperature decrease rapidly for first 200 fathom at the rate 1°F/10 Fathom then it slowed down until 500 fathom and beyond this, drop of temperature is scarcely noticeable. Water never freezes in trenches and 80% of ocean waters have a temperature between 35' and 4W F.
13. The expansion and contraction of sea water due to gravitational pull of Sun and Moon results into rise and fall of surface layer is called tides. The highest tides are called spring tides, generated during Full Moon and new Moon and the lowest tide called neap tide, generate during each quarters of the month so due to vertical position of Sun and Moon to each other. The withdrawal of tide is called ebb.
14. The difference between high tide and low tide water is called tidal range and has a lot of temporal and spatial variation. The tidal force of Moon is most powerful during perigee position causing high tide. Tides are responsible for evolution of amphibians and further terrestrial animals.
15. Ocean currents are of two types; those flow from equatorial regions to pole wards have higher surface temperature and called warm current and those flow equator-ward from polar regions have lower surface temperature are called cold currents. Ocean currents have shown a regular pattern in all the oceans, but North Indian Ocean current shows seasonal reversal of ocean current and Eastern Pacific region occasionally experience anomalies of ocean current.
16. Cold Atlantic Currents: Cayenne current, Florida current, Gulf current, North Atlantic drift, Brazilian current, Labrador current, Irminger Current, canaries current, Benguela currents
17. Warm Pacific Current: Kuroshio Current, North Pacific drift, East Australian current.
18. Cold Pacific Currents: California current, Peruvian current or Humboldt Current
19. Agulhas current, Mozambique current etc are warm Indian Ocean current whereas West Australian current is cold current. North Indian Ocean current reverse direction seasonally.
20. Sargasso sea is an anticyclone circulation of oceanic currents comprising the North equatorial current, the Gulf Stream and the Canary current in North Atlantic Ocean. The water confined in this gyral is clam and motionless. But this kind of similar Sargasso Sea is not found in South Atlantic Ocean. Now this region is concern for unusual algal bloom.
21. As Earth moves from West to East, ocean currents always flows from East to West and are more marked near equator where corriolis force is almost negligible. Northern and Southern oceanic equatorial currents generate counter equatorial current, which is form to fill the water void. Similar, counter currents also flow regularly underneath from polar region to equatorial region and are cold currents.
22. Coral reefs are one of the major biodiversity regions, also called marine rainforest, found in tropical waters and are formed by the accumulation and compaction of skeletons of the lime secreting organisms known as coral polyps. They grow in moderate temperature within the range of 20°C to 21°C.
23. Clean and sediment free water is needed as muddy water can clog the mouth of the reefs. Moderate salinity and the presence of the submarine platform are needed for the growth of the coral reefs. The sequence of the formation of the coral reefs is fringing reefs, barrier reefs and the atolls. Coral reefs developed along the continental margins or along the islands are called fringing reefs. The seaward slope of reef is steep and vertical while the landward slope is gentle.
24. Barrier reefs are partially submerged and are separated from the coast by a much wider and deeper channel or lagoon and sometimes have narrow gaps at several places to allow water circulation from sea to lagoon, are called boat channels. Great barrier reefs in the coast of Queensland, Australia are an example. It is the most extensive type.
25. Atolls are the ring pattern coral islands/reefs formed around a submarine platform or submerged island. Reefs are grown and mid island submerge simultaneously generating such circular reefs. Maldive islands, Lakshadweep islands are example.
26. Coral bleaching refers to the loss of algae from the corals resulting into the white coloration which is indicative of the death of corals.
27. According to UN, sea water is divided into various zones for administrative and economic purpose. These are territorial water, contiguous zone, Exclusive Economic zone and High Sea.
28. Territorial sea extends from base line to 12 nautical miles. The coastal nations have sovereign right over its territorial waters. The next 12 nautical miles are called contiguous zone, where shipment may be possible with permission and no pollution allowed.
29. Exclusive economic zone (EEZ) extends up to a distance of 200 nautical miles from the base line and sovereign countries have exclusive right over economic exploitation of the marine resources, but all countries have navigation rights. Beyond EEZ are high seas where all countries have equal rights.