Plate Tectonics

Plate Tectonics http://education. nationalgeographic

Continental Drift Alfred Wegner—1st to propose the theory of continental drift His theory– Continents were once a single landmass then, over time, they broke up and drifted to where they are today

Wegner’s Evidence of Continental Drift Fossil Evidence Rock formations Climatic Evidence Geographic Evidence

Fossil Evidence

Let’s do a puzzle! Fossil puzzle…match up the fossils on the continents to view Wegner’s evidence of continental drift

Rock Formations Just like fossils, similar rock formations were found on different continents

Climatic Evidence Shows that land used to have different climates than is natural to have in the current position of the land Example: Tropical plant fossils were found in Antarctica

Geographic Evidence Shapes of continents look like they fit together and have similar geographical features

FYI *As continents rift or as mountains form, populations of organisms are separated. When populations of organisms are separated, new species may evolve from existing species. *Similar rock formations and fossil evidence supported Wegener’s evidence.

Mid-Ocean Ridges --a place where crust is spreading an creating new ocean floor --a place where old crust is recycled (this process makes oceanic crust younger than continental crust)

Lets make a mid-ocean ridge! ACTIVITY!!!!!!!!! Lets make a mid-ocean ridge!

Sea-Floor Spreading Harry Hess hypothesized that the valley at the center of mid-ocean ridges was a crack in the Earth’s crust At this crack, magma rises up to form new sea floor which cools and forms new sea flooring This process is known as sea-floor spreading

Layers of our Planet

Layers of our Planet Lithosphere – the solid, outer layer of Earth that consists of the crust and the rigid upper part of the mantle Asthenosphere – The solid, plastic or putty-like layer of the mantle beneath the lithosphere. Made of mantle rock that flows very slowly, which allows tectonic plates to move on top of it

Theory of Plate Tectonics This is the theory that explains how large pieces of lithosphere called plates, move and change shape

Tectonic Plates Scientists have identified about 15 major plates:

Plate Tectonics Activity

Types of Plate Boundaries

Divergent Boundaries These types of boundaries move AWAY from each other Examples: Mid-ocean rifts, the Red Sea (between the African and Arabian Plates)

Convergent Boundaries Plates collide together at these types of boundaries Examples: Areas of subduction Mountain ranges Ocean trenches trench

Transform Boundaries A boundary at which two plates slide past each other horizontally Example: San Andreas Fault in California

The Supercontinent Cycle The process by which supercontinents form and break apart This happens because tectonic plates of the Earth are always moving, though very slowly

450 Million Years ago Near the end of the Precambrian time Earth’s continents were separated…not as much land was above water as today

250 Million Years Ago By the end of the Permian Period, Pangaea had formed

150 Million Years Ago Pangaea had split into two continents, Laurasia and Gondwanaland

60 Million Years Ago Continents were moving toward their current positions on Earth

Future? Scientist propose that in about 250 million years the earth might look like this: