Ancient Knowledge about Oceans

ANCIENT KNOWLEDGE ABOUT OCEANS

An ocean is not just a place where land is covered by water. The ocean floor is geographically distinct from the continents.

1. Geographical Changes Occurring in the Ocean

Geographical processes occurring under the sea not only affect the marine life but also the land regions. The processes that form ocean basins are slow and occur over tens of thousands and hundreds of millions of years. Solid rocks flow into liquid in the blink of an eye. To understand the sea bed, we must learn to follow geologic time.

Geographical conditions are very important to marine biology. Habitats or places where organisms live are directly shaped by geological processes. The shape of the beach, the depth of water, the underlying mud, sand or rock and many other aspects of marine habitat are determined by this geography.

Fertility of oceans by the Equator

Our oceans cover 72% of the earth's surface. As far as the Equator is concerned, about two-thirds of it is found in the Northern Hemisphere. It is only 61% of Ocean. 80% of the Southern Hemisphere is Ocean.

2. Classifications of Ocean Basins

The oceans are traditionally classified into four major basins.

1. Pacific Ocean

It is very deep and very large.

2. Atlantic Ocean

It is slightly larger than the Indian Ocean. But, both have average depths.

3. Arctic Ocean

It is very small and shallow.

4. Mediterranean Sea, Gulf of Mexico and South China Sea

Various such shallow seas are connected to the major ocean basins.

Generally, we divide the oceans into four. But, they are inter-connected. These connections allow sea water, materials and some organisms to move from one ocean to another.

3. Characteristics of Sea Water

The characteristics of sea water are affected by the following three factors.

1. Substances dissolved in water

2. Nature of water

3. Substances that affect the colour of the sea

1. Dissolved solids in sea water come from two main sources

i) Chemical weathering of some terrestrial rocks. They are carried to sea by rivers.

ii) Other materials come from the earth's interior.

2. lons in Sea Water

Usually, only six ions make up 98% of the solids in sea water.

Sodium and Chloride make up about 80%-85% of the solids. These affect the salinity of water. The salinity of water severely affects the organisms living in it.

3. Substances that affect the colour of the Sea

The sea is usually blue in colour. In some places, it is blue- green (or) yellow to brown. The blue colour is the result of many factors.

i) First, water absorbs red light and reflects back blue light.

ii) Secondly, the very small particles in sea water scatter blue light.

Examples for the substances that affect the colour of sea

Dissolved organic matter, Phyto-Plankton living with Chlorophyll pigments and non-living particles such as sea ice and mineral deposits affect the colour of the ocean.

4. Maritime Knowledge of the Ancient Tamil

The ancient Tamils called sea as Kadal, Azhi, Peruneer, Thonneer, Paari, Karkal Othavanam, Thozham. Thirai. They used the sea to the best of their knowledge for trade, seafaring and war.

1. Trade in the Barter Mode

The following Purananooru verse explains that the ancient Tamils did business through barter.

Proof: [Purananooru]

The hunter carrying the deer meat and the cowherd woman carrying the curd gave them to the paddy seller and got paddy in turn.

2. Maritime Trade

During the Sangam period, people were engaged in trade with other Nations by sea using the vessels. This is understood from Sangam literature.

3. Sea Travel

Teak trees felled in Burma and thrown into the sea floated by themselves and reached Danushkoti. They had known the ocean currents. They started travelling by sea using boats, canoes and catamarans. As a result, the business of Tamils crossed the sea, ships of smaller size, ships which carry 3 ton goods were built.