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An important process interconnected with

Earth’s climate history is …

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PLATE TECTONICS

Pangaea Modern Continents

Animation courtesy of U.S. Geological Survey

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Glossopteris FossilPhoto courtesy of U.S. Geological Survey

EARLY SCIENTIFIC HYPOTHESIS - “CONTINENTAL DRIFT”

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Hypothesis : Glossopteris areas were once close together but then

broke apart & moved to the continents’ current positions.

Illustration credit: Peter Bockman

Distribution of Glossopteris plant fossils in Permian (250-299 mybp)

rocks(mybp = million years before

present)

But how do we know this is true?

Are there other possible explanations and

hypothesesfor finding this fossil

plant on widely separated continents?

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Let’s think about this …ACTIVITY 1: Hypothesis Helper

Which of the five species (if any) might provide the

best evidence for tectonic plate

movement?

Which species could have spread between Africa &

South America only if those continents were

once connected?

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Not the species that could have reproduced across the

ocean …

NOPE!

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… but the species that could have spread only on continuous

land which later broke apart

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A - Large triangular leaves; berries commonly

eaten by migratory animals B - Short, narrow, oval leaves; produces fewseeds, reproduces mainly by stolons C - Small thin feathery leaves; large seeds havespongy outer cover, allowing seeds to float andtravel easily in either fresh or salt water D - Thrives in swampy or watery environments;very large, heavy seeds sink and lodge inbottom sedimentsE - Long thin leaves; small fluffy seeds easilycarried by wind

stolons

WOOHOO!You have used ancient plants’ adaptations for reproduction & seed

dispersal (seed transport) to test a hypothesis about tectonic plate

movements!

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HOW DO THE SCIENTISTS KNOW SO MUCH ABOUT THEM?

IF THOSE PLANTS ARE FOSSILS &

ANCIENT & PROBABLY EVEN

EXTINCT …

WHOA!JUST A

SECOND!

I HAVE A QUESTION!

Earth processes that operated in the past are similar to those operating today.

“The present is the key to the past.”

PRINCIPLE OF UNIFORMITARIANISM

(UNIFORMITY)

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So earth scientists study modernvolcanoes to understand ancientvolcanic rocks … And modern rivers, glaciers, deserts,& coastlines and their sediments tounderstand how ancient sedimentaryrocks formed … And modern plants & their adaptationsto understand similar ancient plants &their adaptations.

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Based on its fossilremains and oncertain similaritiesto modern BaldCypress, scientistshave interpreted:

Tree shape & roots like modern bald cypressWarm, very wet environmentsSeeds too fragile to survive a long sea trip

FOR GLOSSOPTERIS, WHICH HAS NO MODERN REPRESENTATIVES

GLOSSOPTERIS

BALD CYPRESS

Illustration credits: Glossopteris, Rose Prevec, Rhodes University (South Africa); bald cypress, NRCS