4.1 & 4.2 Plate Tectonics

As explorers began bringing back information about the world, map makers began to notice the coastlines of continents could possibly be matched up…… Where the continents once touching???? This led to the formation of a hypothesis.

Continental Drift Hypothesis that continents had moved. – Pangaea: single landmass – Panthalassa: all seas

Evidence for Continental Drift 1)Fossils of plants and animals in areas that would have been joined in Pangaea 2)Similar age and types of rocks South America (Brazil) and Africa

Evidence of Continental Drift 3) Sea floor Spreading Mid Ocean Ridges 4) Paleomagnetism

3) Seafloor spreading Newest rock is found at mid ocean ridges The mid ocean ridges are breaks where magma flows up from with in the earth forming new rock. Ocean floor is moving away from these rifts

Journal: Seafloor spreading Where is the newest (youngest) oceanic rock found in the diagram? Where is the oldest oceanic rock found in the diagram? AB C

Journal In your own words, describe seafloor spreading:

4) Paleomagnetism As magma solidifies, the iron in it aligns with earth’s magnetic field. As earth’s poles switched, the iron bands polarity switched as well. There is a pattern on each side of a mid ocean ridge which shows that the sides where formed at the same time and then spread out!

The Theory of Plate Tectonics Describes continental movement and proposes an explanation – 2 types of Crust Oceanic & Continental which make up the lithosphere – Below the lithosphere is the asthenosphere which had the ability to flow.

The Theory of Plate Tectonics The pieces of lithosphere float on top of the asthenosphere

What causes plate motion??? Convection Currents: warm material rising, cool material sinking – Based on density differences – Less dense materials rise (warm magma) – More dense materials sink (cool magma)

What causes plate motion??? In plate tectonics, -cycle of warm magma rising up to the lithosphere where it cools and solidifies -The new lithosphere moves away from the mid ocean ridges -It cools and becomes more dense -It eventually is subducted into the asthenosphere

3 main types of Plate Boundaries Divergent Convergent Transform/ Transverse Journal – What does the word diverge mean? – What does the word converge mean?

Journal: Boundaries DivergentConvergentTransform/ Transverse

Divergent Boundaries Two plates moving away from each other Forms: – Rift Valley (Continental/Continental) – Mid Ocean Ridges (Oceanic/Oceanic)

Convergent Boundaries The direct collision of two plates – Oceanic-Continental Form subduction zones and volcanoes – Continental-Continental Form mountains – Oceanic-Oceanic Form Island arcs

Transform/Transverse Boundaries When two plates move past each other – Form Faults – Can you name a famous local fault???

Microplate Terranes Continents are a patchwork of terranes Terranes: pieces of lithosphere – Own geological history – Separated by faults at its boundaries – Own magnetic properties

On a separate piece of paper…. Quiz yourself: 1.Name and describe the 3 types of plate boundaries. 2.At what type of boundary would island arcs be found? 3.What is the evidence for continental drift?