Plate Tectonics

ESPS 2015

Hagen

ESSENTIAL QUESTIONS

Explain and give evidence of Continental Drift

Describe the process of sea-floor spreading

List and analyze the 3 types of boundaries

https://www.youtube.com/watch?v=zocutif0cQY

Give one piece of scientific evidence that is true

and one piece that is false

SPONGE ACTIVITY

Why do Continents Drift?

Earths crust is not a uniform covering, its made of 8 major and minor plates – North American/Pacific/Juan de Fuca plate

As these plates move, the continents are rafted along passively (like a piggyback ride on top of Aesthenosphere, which is on top of the mantle

1960’s the Theory of Continental Drift or Plate tectonics became established

Continental Drift

1900’s-----1912

Alfred Wegener first proposed the theory of continental drift. Wegener provided evidence that the there was once a giant land mass, but did not explain how the continents moved

His theory stated that the continents used to be one large super-continent or “Pangea” and through time they have broken apart and moved.

Continental Drift• Wegener hypothesized that there was a gigantic supercontinent 200

million years ago, which he named Pangaea, meaning "All-earth".EVIDENCE!!!!!! Give some space below each type of evidence1. Continental Fit – Example of South America and Africa.

2. Fossils – Fossils in S. America and Africa Dated the same

3. Glacial Patterns – Glacial scars on N. America and Asia/Europe that had the same dates

http://www.classzone.com/books/earth_science/terc/content/visualizations/es0806/es0806page01.cfm

Continental Drift Evidence:

When you look at a map you can see the how the edges of continents fit together like a puzzle

The theory of continental drift states that continents have moved from their current locations and will continue to move over time

Tectonic plates move with speed ~1 cm/year to ~10 cm/year.

The speed is different from plate to plate, and can depend on how much active the plate currently is.

Continental Drift Evidence

Fossils show that the same reptiles lived on different continents

despite being so far apart. Plants too.

Continental Drift Evidence

Geological features show that colder climates were once warmer and warmer climates were once cold (e.g. glaciers and plant fossils)

Rock clues show the same rock features on different continents

Evidence Activity

Cut out continents and thenCut out continents and then

paste them on the mappaste them on the map

Be sure to match up fossilBe sure to match up fossil

evidence with rock and desertevidence with rock and desert

evidenceevidence

Homework tonight

Case of the Mesosaurus

Continents today

Seafloor SpreadingAt one time the bottom of the ocean was a foreign as space; with the discover of using sound waves to map the ocean floor lead to amazing discoveries

A system of ridges and valleys was discovered running through the center of the Atlantic Ocean

Sea floor spreading is the process by which new sea floor is created, pushing two tectonic plates further apart

Seafloor SpreadingAs scientists began studying the ages of the ridge they found that as they moved towards the center of the ridge the rocks got younger and younger

This means that new rock was forming at the center of the ridge and being pushed outwards as new rock filled in

Seafloor SpreadingEvidence of Seafloor spreading:

The rocks age as they move away from the ridge

The new rock contains iron which is magnetic; over the course of the Earth’s history the magnetic poles have switched; when the iron in the rock cools it lines up with the pole; the iron samples have reversed several times

Theory of Plate TectonicsWith the discovery of seafloor spreading showed more than why the continents are the way they are – they showed why we have the geological features that we do

The Theory of Plate Tectonics combines continental drift and seafloor spreading and states that there are several plates that move around the mantle of the Earth

Theory of Plate TectonicsWhere two plates interact are called plate boundaries3 types of boundaries are called divergent, convergent and transformThese boundaries form earthquakes and volcanoes Divergent boundaries move apart and cause seafloor spreading

Theory of Plate TectonicsConvergent boundaries move together and form volcanoes

Ocean – ocean boundaries (hot spots)

Ocean – continental boundaries (magma chambers)

Continental – continental boundaries (mountains)

Transform boundaries move past one another and form earthquakes

Theory of Plate Tectonics