- Mesozoic,Paleozoic and Cenozoic eras
- Two major climate changes characteristic of each era you show on your timescale and
mention any changes to plant and animal life that took place during this time.
Continental Drift DUMMY
Continental driftis the breakup and movement of the Earth’s continents relative to each
other by drifting across the ocean bed. Since the initial continental drift hypothesis was
proposed, the study of plate tectonics has helped us understand why continents move.
Plate tectonicsis the study of the folding and faulting of the Earth’s crust (lithosphere).
Biogeographyis the branch of biology focusing on the geographical distribution of plants
and animals. It has been instrumental in developing our understanding of the evidence for
continental drift.
Evidence for continental drift
There is considerable evidence for the theory of continental drift that draws upon fossil
evidence, plate tectonics theory and studies of glacier sediments. For example:
- Similar plant and animal fossils have been found on different continents’ shores, sug-
gesting that these were once joined. For example:- TheMesosaurusfound in Brazil and South Africa.
- TheLystrosaurusfrom rocks of the same age found in South Africa, South Amer-
ica, India, Australia and Antarctica - Earthworms found in South America and Africa suggest that these existed in a
common habitat on a single continent.
- By studying the complementary arrangement of South America and Africa and the
manner in which these pulled apart due to various plate tectonic forces scientists have
been able to confirm the hypothesis of continental drift. - The study of glaciers left over from the ice ages has provided an important line of
evidence for continental drift. Glacial sediments from South America, Africa, India,
Madagascar, Arabia, India, Antarctica and Australia showed evidence of having once
been joined together, suggesting the existence of the supercontinent Gondwana. - Fossil evidence for Pangaea includes plant and animal fossils.
Using this evidence, scientists have inferred that in the past the Earth existed as a super-
continent known as Pangea until the early Mesozoic era. There were three major phases in
the break-up of Pangea:
- First phase: about 175 million years ago, Pangea began to rift, giving rise to the super-
continents Laurasia and Gondwana. - Second phase: began in the early Cretaceous period (150–140 million years ago) when
Gondwana broke and separated into multiple continents: Africa, South America, India,
Antarctica and Australia. - Third phase: occurred in the early Cenozoic era. During this phase, Laurasia split
when North America/Greenland split from Eurasia resulting in the expansion of the
Chapter 11. History of Life on Earth 317