|How can fossils be found on different continents?|
|Question Date: 2018-11-15|
Fossils, the remains or traces of ancient living
things, are preserved in sedimentary rocks,
that form the recycled fragments of other others.
The remains of organisms sometimes getting buried
in sediments (such as mud, sand, gravel) after
their demise. Given enough time and the right
conditions, those sediments are transformed into
sedimentary rock, and any biologic material they
contain turns into a fossil.
Since sedimentary rocks occur on every continent,
it's not surprising that fossils are found
globally. Bear in mind, that not all fossils
are the same age, and that the continents weren't
always arranged as they are today. Therefore,
what kinds of fossils we find where is a
complicated story. These complications explain
why, for example, it's nearly impossible to find
dinosaurs in California.
Thanks for an interesting question!
Continents have changed their positions
throughout Earth's history due to plate
tectonics. When we find the same types of
fossils from the same time on different
continents, it is often an indicator that the
continents were connected at that time.
Alternatively, if we find very similar fossils
that are not quite the same, it is possible that
both continents had similar environments and that
two different species separately adapted to those
environments with similar results. This is known
as convergent evolution.
Different animals and plants live in different
parts of the world. You know this already: deer
live in North America and northern Eurasia,
elephants live in Africa and in southern Asia, and
kangaroos live in Australia. When an animal or
plant dies and gets fossilized, it gets fossilized
in the continent where it lived and died. As a
result, the paleontologists of the future will
find fossils of deer in the northern hemisphere
and fossils of kangaroos in Australia.
The same was true in the past as well.
Tyrannosaurs lived in North America. They did
not live in South America. South American fossils
of that age include different kinds of dinosaurs,
but not tyrannosaurs, because they did not live
Of course, the continents themselves
move, too. It is possible now to walk from
North America to South America, but not in the
days of tyrannosaurs; South America was an
island continent then, much like Australia is
now. Meanwhile it was possible to walk from
Australia to Antarctica then, because they were
part of the same continent. This means that the
animals living in Australia and Antarctica then
are found in both continents, since they were
the same even though the two continents today are
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