CHAPTER TENPLATE TECTONICS

Background Information

The Earth is made up of several layers that have different properties and compositions.

There are three main layers: Crust Mantle Core (inner and outer)

Layers of Earth

Section 1: Continental Drift

Alfred Wegener (German meteorologist) Suggested that all the continents were

joined together at some times in the past 1912: he proposed the hypothesis of the

continental drift which explains that continents have moved slowly to their current locations over time

Pangaea (“all land”) is the name he gave to the large land mass that he believes existed over 200 million years ago

Evidence of Continental Drift

Section 1: Continental Drift

Evidence of Continental Drift

Section 1: Continental Drift

Evidence of Continental Drift Fossil

The reptile Mesosaurus was found in South America and Africa

Fossils from a fernlike plant Glossopteris was found in Africa, Australia, South America and Antarctica

Climate Fossils of warm weather plants were found on

an island in Arctic Ocean Glacial deposits and grooved bedrock were

found on South America, Africa, India, and Australia

Evidence of Continental Drift

Section 1: Continental Drift

Rock Similar rock structures and types of rocks are

found on different continents Appalachian Mountains (below left) in eastern

United States are similar to mountains in Greenland and Western Europe (below right)

South America and western Africa have similar rock structures

Evidence of Continental Drift

Section 2: Seafloor Spreading

Harry Hess (1960) Proposed the new idea of seafloor

spreading to explain how the continents could move.

Seafloor spreading is when a hot, less dense material is forced up through the Earth’s crust in an opening called a mid-ocean ridge, it turns and flows sideways, carrying the seafloor away from the ridge in both directions.

Mapping the Ocean Floor

Section 2: Seafloor Spreading

Evidence for Seafloor Spreading: Age evidence:

Rocks on sea floor – near mid-ocean ridge – were 180 million years old or younger

Rocks away from mid-ocean ridge – near continents – some were almost 4 billion years old

Magnetic evidence: Scientists found that rocks on the ocean floor

show many periods of magnetic reversal.

Mapping the Ocean Floor

Section 3: Theory of Plate Tectonics

Seafloor spreading let scientists know what was happening with the crust and upper mantle.

1960 – scientists developed a new theory that put continental drift together with seafloor spreading.

Theory of Plate Tectonics: Earth’s crust and upper mantle are broken into sections. Theses sections – called plates, move around on a layer of the mantle.

Plate Tectonics

Section 3: Theory of Plate Tectonics

Plates are made of the crust and a part of the upper mantle.

The lithosphere is a rigid layer that is generally less dense than material that is underneath.

The plastic-like layer below the lithosphere is called the asthenosphere.

Plate Tectonics

Section 3: Theory of Plate Tectonics

3 kinds of plate boundaries: Divergent Boundary: boundary between

plates that are moving apart

Plate Boundaries

Section 3: Theory of Plate Tectonics

3 kinds of plate boundaries: Convergent Boundary: Boundary

between plates that are moving togetherArea where one plate goes down into the

mantle is called the sub-duction zone. Volcanoes usually form near convergent

boundaries when the rock melts or mountains can form when two plates collide and crumple up.

Plate Boundaries

Section 3: Theory of Plate Tectonics

3 kinds of plate boundaries: Transform Boundary: boundary where

plates are sliding past each other.

Plate Boundaries

Section 3: Theory of Plate Tectonics

Process of heating and cooling, which causes movement of particles is called convection current.

Effects of Plate Tectonics: Plates are constantly interacting with

other plates. Forms mountain ranges, volcanoes,

faults, rift valleys

Causes of Plate Tectonics