Plate tectonics

Lithosphere
Earth’s lithosphere or “skin” has tectonic plates
Currently there are 12 large plates and several smaller ones

Put the Plates on the Mantle!
These plates rest on a layer of rock called the mantle.
The mantle moves very slowly, dragging the tectonic plates on top of it.

Plates move as fast as your fingernails grow! (only 2 - 5cm per year)
Over a very long period of time this can amount to thousands of miles of movement

Plate Boundaries
TRAnsform Boundaries = plates slide horizontally (plates TRAvel side by side)
DIVergent Boundaries = plates move apart (plates DIVide or plates DIVorce)
COnvergent Boundaries = plates move toward each other (plates COme together and COllide)

TRAnsform Boundaries
Two plates that TRAvel side by side can cause an earthquake

DIVergent Boundaries
Plates that DIVide produce a “rift” – a giant crack
If a rift tears apart a continent and widens for millions of years, a new sea forms (and can gradually form a new ocean)

COnvergent Boundaries
When two continental (land) plates COme together, a mountain belt is formed
But when a continental plate COllides with an oceanic plate, the oceanic plates sinks and melts rock. Then the molten rock rises and forms a line of volcanoes

Continental Drift
As tectonic plates move, they carry the continents (with rocks and fossils) along with them
Continental drift = describes how continents have moved over Earth’s surface
Untold Tragedies of Continental Drift

Geologic Evidence of Continental Drift
Rocks in India have glacier scratches and scars so ice must have once covered India
South Africa and Brazil have ice-scratched rocks of the same age… and so at one time they were all probably joined

Fossil Evidence of Continental Drift
Common fossils are found on continents that are now separated by oceans.
Mesosaurus fossils are found in South America and Africa.
Today these 2 continents are separated by 3,000 miles of ocean (too far to swim!)
Mesosaurus must have lived at a time when the 2 continents were joined

History of Continental Drift
Looking at a map of the Earth, it seemed that the continents could fit together like a jigsaw puzzle.
Alfred Wegener came up with the idea of "continental drift."
Wegener suggested that a single "supercontinent" called Pangea once existed in the past.

Changes in Climate
Continents that have drifted closer to the equator are warmer because the sun’s rays hit them directly.
Continental drift also changed the flow of ocean currents and wind flows.

Changes in Life
As environments changed, so did the organisms
Life on land changed as continents drifted apart
Sea life changed as new oceans were formed
Changes in climate led to new adaptations