Category Geology

How were the oceans formed?

         About three-fourth of the Earth’s total surface is covered with water. Only one-fourth of Earth’s surface is land. The total area of the Earth’s surface covered by oceans comes to 361.100 million sq. km. Do you know how and when these oceans were formed?

          It is not yet fully known when oceans were formed. However, at the beginning of the formation of Earth, there were no oceans. The age of oceans has been calculated on the basis of the minerals present inside them. It is estimated that oceans were formed some time between 500 to 1,000 millions years before.

            The story of the origin of oceans is very interesting. The Earth was a giant burning fire ball at the time of its birth. Its surface was formed by molten rocks. When the Earth started cooling slowly, it was enveloped by clouds of gases. These clouds became very heavy after cooling. They started raining heavily, but the Earth’s surface was still so hot that the raindrops falling on it would evaporate and mix with the atmosphere again. This would again come down to the Earth in the form of rains. This cycle continued for millions of years. The Earth’s crust became cold and tough and the rain-water would boil no more, but the heavy down-pour continued for thousands of years. The low-lying areas of the Earth were filled up with the water of these heavy rains. These vast lakes of water on the surface of the Earth are today’s oceans. 

What is Dead Sea?

          Dead Sea is the only sea on earth which has no plant or animal life. It is, therefore, appropriately called Dead Sea. In fact, Dead Sea is a saline lake situated between Jordan and Israel. This is 77 km long and its breadth ranges between 5 to 18 kilometres. The water level of Dead Sea is the lowest on the Earth. It is lower than the sea-level by 396 metres. Millions of years ago the level of Dead Sea was, however, higher than the present one by 427 metres. At that time aquatic animals were living in Dead Sea. All of a sudden, there was a draught and the water of this sea evaporated. Gradually this sea acquired the present state.

          No river originates from this sea. The Jordan River and some small canals end up in this sea. Since no river comes out of this, the water of this sea depletes only by evaporation. Consequently, the amount of salt and other soluble minerals brought into the sea by the Jordan River and other smaller canals goes on increasing. You will be surprised to know that the amount of salt present in Dead Sea is the largest in comparison to the other seas. In general, the amount of salt present in any sea is 4% to 6%. But even this make you sick as it contains large quantities of magnesium chloride and other poisonous substances. Due to the presence of large quantities of salt and other poisonous materials no living being can survive in this sea. Hence fish and other acquatic animals of the Jordan River die as soon as they enter the water of this sea.

 

 

Are there mountains inside the sea?

          Generally, Sea Mountains are those mountains which are at least one kilometre above the seabed. A number of such mountains have been discovered.

          Upheavals at the bottom of the sea are responsible for the formation of these mountains. Volcanic eruptions in the seabed also make mountains. Generally, these mountains are one to three kilometres high. Majority of these mountains remain submerged in water, but some of them have surfaced above also. The flat mountains coming above water are called islands. The Hawaii islands were formed in this manner.

          There are many mountains in the midst of oceans. The mid-ocean ridge is continuous and it winds for 60,000 km through all worlds’ oceans. There are many mountains in the north-east part of the Pacific Ocean. Most of these mountains are submerged in water, but some of the mountains of the Hawaiian chain have surfaced above. They are called the Hawaii Islands. The highest mountain of the Hawaiian chain is the Mauna Kea. The height of this mountain is 4,200 metres above sea level, but the total height of this mountain from the bottom of the sea is 9,686 metres. That means the height of this mountain inside the sea is 5,486 metres. If its height is taken in full, this is the highest mountain of the world. 

What causes monsoons?

           The word monsoon is used to connote a seasonal wind which flows with consistency and regularity for one part of the year and blows from the other direction for the other part of the year.

            Monsoon rains are generated over different parts of the world due to the difference in response of land and sunlight and the resulting wind movement.

            Over land, as a consequence of chemical composition and structure of the soil, only a few centimeters of the soil is heated by sunlight. But as the air has a low heat capacity, the atmosphere gets heated up rapidly.

            On the other hand, the sea is warmed up slowly because of its larger heat capacity and also because sunlight penetrates up to 200 m into the water. Hence the air above the oceans remains cooler. The temperature difference between them lies in the range of 5-10 degrees Centigrade.

            As a consequence of this, the warmer air over land begins to rise. To compensate this ascending air the denser air from the ocean has to move towards the land. (This is commonly known as sea breeze). This differential heating is the driving force for the monsoon winds.

            During the northern summer (summer in the northern hemisphere) the sun is over the Tropic of Cancer (23.5 degrees). In this period the land in the northern hemisphere gets warmed up while the southern hemisphere is cooler as it receives less sunlight.

            The land-sea contrast is much more in rectangular region shown in the figure than any other part of the world. Due to differential heating, the cooler moist air from the southern hemisphere starts moving towards the hot northern hemisphere. Once this airflow (called Somali current because it flows along the coast of Somali and Kenya region) crosses the equator the Coriollis force (a force arising due to the rotation of the Earth) turns the air to its right (in the Northern hemisphere). This flows over India and East Asia from the South West direction (hence the name south west monsoon). This moist air when aided by other factors results in abundant rain.

            The Tibet Plateau on the Himalayas acts as a potential heat source for this kind of air movement. The lifetime of south-west monsoon is about 100 days which starts early June and ends by mid September. The arrival of monsoon is a gradual process starting with a transition period when the atmospheric characteristics change from a state of extreme dryness to high humidity and slight rainfall. Thunderstorm is a feature of pre-monsoon months of April and May over North-East India.

How is depth of ocean measured?

Ultrasonic sounds are used to measure the depth of oceans and the principle behind is known as sound navigation and ranging, Sonar. Ultrasonic waves are sent from a transmitter from the surface of the sea, from a ship.

            The sound waves are reflected by the sea bottom are sensed be a receiver system and recorded. With the known value of the speed of sound in water, and the time taken by the sound to travel from the surface to the bottom and back, the depth is measured.

Why is paleontology important in the study of evolution?

Paleontology is the study of fossils. Paleontology has played a key role in developing the theory of evolution. The study of fossils has shown that the animals and plants of prehistoric times were very different indeed from the animals and plants of today. By reassembling fossils bones, scientists can get an idea of the size and shape of the creatures that inhabited the Earth before the appearance of humans. Teeth and shells that have been fossilized also tell us much about the lifestyle of these creatures. Fossils of insects are often found embedded in amber, which is a transparent rock nodule formed when the resin from trees petrifies. Small creatures are sometimes trapped inside the amber, and are perfectly preserved to give us a glimpse of ancient insects.Trace fossils are also important in the study of evolution. Trace fossils are tunnels, worm casts and tracks that animals have made on soft sediment that has later hardened into rock. These imprints of animals on the move reveal much about the lives of ancient species, including their size, gait, stride length, and speed.