Continental Drift, Pangea, and Plate Tectonics

Evolution and Genetic

Warm up: write the answer in your notebook.

A dolphin is a mammal that must come up to the water’s surface to breathes. A shark is a fish that breathes

underwater. Yet the dolphin and the shark have similar body shapes. Are those body shapes analogous or homologous?

Explain your answer.

Introduction● The Earth’s movement and the shape of Earth’s surface give us

evidence to evolution.○ Continental Drift○ Plate Tectonic Theory○ Boundary Movement○ Pangea

Alfred Wegener - create the concept of the supercontinent

● Wegener believed that long ago all of Earth’s continents were joined together in one large landmass, now referred to as Pangaea.

● Wegener believed that Pangaea broke apart and then, over a long period of time, the continents moved to their present positions.

● He focused his attention on three points: ○ the shapes of the continents ○ the locations of matching fossils○ the comparison of plant fossils with the climates in which they were

found.

Evidence to support the Earth’s movement

● Fossils of the same animals had been found on different continents that are today separated by oceans.

● Fossils of tropical plants had been found in Antarctica.● Shapes of the continents match.

Alfred Wegener - Continental Drift

● The continental drift state that the continents used to be one supercontinent called “ Pangea”.

● Continental drift was an earlier theory that does not explain how and why the continents moved. ○ Today, scientists know that continental drift is driven by convection

currents beneath Earth’s lithosphere.

Plate Tectonic Theory

● On a map of Earth, you may have noticed that the continents almost look like puzzle pieces.

● Plate tectonic theory states that the Earth’s crust is divided into several plates.○ The constant movement of the plates is responsible for geological events

such as volcanic activity, earthquakes, and continental drift.● The continents move very slowly, they can move thousands of

kilometers over millions of years.

How did the theory of plate tectonics originate?

● Observations and evidence:○ many coastlines on opposite sides of the ocean

appeared to match up liked puzzle pieces.

○ matching fossils found on different continents

Plate Tectonics

Types of Boundaries Movements

● Many geologic features—including mountains, volcanoes, and trenches—are formed at the boundaries where plates meet.

● Events such as earthquakes and the formation of new ocean crust also happen at plate boundaries. A. Convergent boundariesB. Divergent boundariesC. Transform boundaries

Plate Boundaries

● Divergent boundary occurs when two tectonics plates move away from each other.○ Lava spews from long fissures and geysers spurt superheated water

○ Frequent earthquakes strike along the drift.

○ Beneath the rift, magma rises from the mantle.

Convergent Boundary● Convergent boundary occurs when two plates

come together.○ The impact of the two colliding plates buckles the

edge of one or both plates up into a rugged mountain range, and sometimes bends the other down into a deep seafloor trench.

○ A chain of volcanoes often forms parallel to the boundary.

○ Powerful earthquakes occurs.○ Magma rises into and through the other plate,

solidifying into new crust.

Transform Boundary

● Two plates sliding past each other forms a transform plate boundary.

○ Rocks that line the boundary are pulverized as the plates grind along, creating a linear fault valley or undersea canyon.

○ Earthquakes rattle through a wide boundary zone.○ No magma is formed.

Harry Hess - Seafloor Spreading

● Harry Hess built on Wegener’s work to develop an explanation for continental drift.

● While studying the bottom of the ocean, scientists found places where the seafloor had split apart and new rock formations had appeared.

Seafloor Spreading

- Magma from under the seafloor had risen, and as the magma cooled it formed new rock.

- The older rock on either side of the seafloor split had been pushed apart, causing the seafloor to spread.

- Like ripples spreading from the center of a pool, new rock had formed and pushed the older rock outward.

Review

3D Interactive Earth Globes

Plate Movement Interactions

Dance of the plates