PLATE TECTONICS, EARTHQUAKES, AND THE STRUCTURE OF THE EARTH

GOALS FOR THE LECTURE Students will write and discuss various ideas related to the physical structure of the Earth (9C, 10A, 10B, 10C, 10E, 10F) Students will write and discuss ideas related to plate tectonics, as well as follow its progression through history(10D)

WHY DOES THE EARTH LOOK LIKE THIS? Where did the tectonic plates come from? They came from the ancient land masses the used to cover the Earth

HISTORY Has the Earth always looked like this? What did the Earth look like in the past?

HISTORY What name do we give this place? Pangea When was this? 200 million years ago (mya) Before there was Pangea, the Earth looked even less like it does today

HISTORY About 160 mya, Pangea began to break apart. Laurasia and Gondwanaland were the dominant land features.

HISTORY About 120 mya, Laurasia and Gondwanaland began to break apart. Continents we might recognize were the result.

HISTORY 80 mya, Madagascar breaks off from India as India begins its race across the Indian Ocean.

HISTORY 40 mya, Inland seas in the North American Plate and Asian plates drained and India began to push up the Himalayan mountains.

TODAY

FOSSIL EVIDENCE Organisms have left fossil evidence of their existence on continents across oceans. Originally thought to be caused by organisms traveling across the ocean on “Rafts.”

FOSSIL EVIDENCE Other theories suggested organisms crossed over land bridges that were once exposed.

FOSSIL EVIDENCE A 3 rd theory surfaced known as Island stepping stones.

EVIDENCE THAT THIS IS WHAT REALLY HAPPENED…

CONTINENTAL DRIFT Alfred Wegener publishes The Origin of Continents and Oceans in Proposes that the continents were once all part of a large landmass called Pangea, and then drifted apart.

CONTINENTAL DRIFT This idea matured into our current theories of Plate Tectonics The surface of the earth is divided into about 20 plates.

PLATE TECTONICS All plates contain both continental and oceanic crust. This is a major departure from continental drift.

THE THEORY Plates are rigid structures and will always move as a distinct unit. The distance between two points on a tectonic plate will always be the same

LITHOSPHERE The layer of solid rock that surrounds the Earth and a thin layer of molten rock beneath it.

ASTHENOSPHERE The molten rock beneath the lithosphere.

WHERE DO THINGS CHANGE? At the boundaries between plates. 3 categories Divergent Convergent Transform

DIVERGENT

WAIT NO…

DIVERGENT BOUNDARIES Occur at oceanic spreading centers, typically called “Mid-Ocean Ridges” 2 “Plates” are being pulled apart by magma from underneath that is pushing upwards Process known as Seafloor Spreading

CONVERGENT BOUNDARIES 3 classifications of Convergent Boundaries Oceanic-Continental Oceanic-Oceanic Continental-Continental

CONVERGENT BOUNDARIES Subduction Zone(vocabulary)- the place where one tectonic plate rides up over another and causes it to be pushed down and recycled (melted)

CONVERGENT BOUNDARIES Oceanic-Continental Result in the formation of Volcanic Arcs along the boundary

CONVERGENT BOUNDARIES Oceanic-Oceanic Result in the formation of Island Arcs Chains of volcanic islands that form along oceanic plate boundaries

CONVERGENT BOUNDARIES Oceanic-Oceanic boundaries will also result in the formation of Trenches These are places where the ocean is deeper than the surrounding area due to subduction.

CONVERGENT BOUNDARIES Continental-Continental Result in the formation of mountain ranges made from deformed (squeezed) native rock

CONVERGENT BOUNDARIES

TRANSFORM BOUNDARIES Plates move in opposing directions on either side of the boundary.