SCIENCE NOTES UNIT 2 Plate Tectonics

Section 1: Continental Drift Continental Drift

Pangaea : means “all land”; a large ancient landmass that was composed of all the continents joined together Continental drift : continents were once all connected and have moved slowly to their current locations

1.Continental Drift Theory 2.Similar fossils on different continents 3.Rocks of same age on different continents 4.Evidence of a Mid-Ocean Ridge Evidence for Pangaea

Animal Fossil Evidence Animal fossils of the same species have been found on different continents. These animals only lived in freshwater or on land, they would not be able to swim between the continents

Plant Fossil Evidence The presence of the same species of plant fossils in so many areas; all of these regions must have been connected and had similar climates.

Rock Evidence Similar rock types are found on different continents.

Wegner couldn’t prove HOW the continents drifted apart. Evidence for Pangaea

Plate Tectonics

plate: a large section of Earth’s lithosphere (oceanic or continental crust and rigid upper mantle) that move around on the asthenosphere plate tectonics: theory that Earth’s outer layer is broken into plates that float and move around on the mantle

Divergent Boundary 1.) Continental-Continental Two plates move apart Example: The Great Rift Valley in Africa (2 situations)

Divergent Boundary 2.) Oceanic-Oceanic Two plates move apart, magma seeps up, fills gap and hardens Example: Mid-Atlantic Ridge (seafloor spreading)

Convergent Boundary Where two plates come together Subduction zone : the area where an oceanic plate subducts or goes down into the mantle (3 situations)

Convergent Boundary 1.) Oceanic-Continental The more dense oceanic subducts under the continental plate Creates a deep-sea trench and volcanoes on the continental side Example: Andes Mountains

Convergent Boundary 2.) Oceanic-Oceanic The older, denser oceanic plate subducts under the other Creates trenches and volcanoes can become islands Example: Mariana Islands, Japan

Convergent Boundary 3.) Continental-Continental Two plates collide and crumple up Forms mountain ranges No volcanoes because no subduction Example: The Himalayas Mt.Everest

Transform Boundary Where two plates slide past each other causing earthquakes Example: San Andreas Fault

3 Type of Boundaries