Answer:
2. Indications of severe climatic change. (Ancient climate).
What evidence did support Alfred Wegener’s continental drift theory?
Continental drift theory propounded by Alfred Wegener in 1920’s broke myth of permanency of earth surface. According to the theory, there existed one big landmass which he called Pangaea covered by one big ocean called Panthalassa.
A sea called Tethys divided the Pangaea into two huge landmasses: Laurentia (Laurasia) to the north and Gondwanaland to the south of Tethys.
Drift started around 200 million years ago (Mesozoic Era), and the continents began to break up and drift away from one another and occupied present position as shown below.
The drift was in two directions-
1.
equator wards due to the interaction of forces of gravity, pole-fleeing force and buoyancy (ship floats in water due to buoyant force offered by water), and
2.
westwards due to tidal currents because of the earth’s motion (earth rotates form west to east, so tidal currents act from east to west
Evidences in support of theory are
1) Affinity of physical features (Jig saw fit)
Ex: South America and Africa (especially, the bulge of Brazil fits into the Gulf of Guinea
Greenland and Ellesmere and Baffin islands
The east coast of India, Madagascar and Africa
North and South America on one side and Africa and Europe on the other fit along the mid-Atlantic ridge.
2) Fossil deposits
The observations that Lemurs occur in India, Madagascar and Africa led some to consider a contiguous landmass “Lemuria” linking these three landmasses.
Mesosaurus was a small reptile adapted to shallow brackish water. The skeletons of these are found only in South Africa and Iraver formations of Brazil. The two localities presently are 4,800 km apart with an ocean in between them.
3) Botanical evidence
Presence of glossopteris vegetation in carboniferous rocks of India, Australia, South Africa, Falkland Islands (Overseas territory of UK), Antarctica, etc. can be explained on the basis of the fact that parts were linked in the past.
4) Rocks of same age across continents
The belt of ancient rocks of 2,000 million years from Brazil coast matches with those from western Africa.
5) Tillite deposits
It is the sedimentary rock formed out of deposits of glaciers. The Gondwana system of sediments from India is known to have its counter parts in six different landmasses of the Southern Hemisphere. At the base the system has thick Tillite indicating extensive and prolonged glaciation. Counter parts of this succession are found in Africa, Falkland Island, Madagascar, Antarctica and Australia besides India.
6) Placer deposits - Rich placer deposits of gold are found on the Ghana coast (West Africa) but the source (gold bearing veins) are in Brazil and it is obvious that the gold deposits of the Ghana are derived from the Brazil plateau when the two continents lay side by side.