Liz LaRosa http://www.middleschoolscience.com 2009 Plate Tectonics Liz LaRosa http://www.middleschoolscience.com 2009

Earth’s Layers The Earth's rocky outer crust solidified billions of years ago. This crust is not a solid shell; it is broken up into huge, thick plates that drift atop the soft, underlying mantle. It is less dense than the mantle, so it floats on top of it.

difference in thickness between the Oceanic & the Continental crust! The Crust Look at the difference in thickness between the Oceanic & the Continental crust! Outermost layer 5 – 100 km thick Made of Oxygen, Silicon, Aluminum

The Mantle Lies between the crust and the core Contains most of the Earth’s mass Has more Mg and less Al and Si than the crust Crust + upper mantle=Lithosphere

The Core Below the mantle and to the center of the Earth Believed to be mostly Iron, smaller amounts of Nickel, almost no Oxygen, Silicon, Aluminum, or Magnesium

Tectonic Plates

Plate Tectonics Greek – “tektonikos” =“of a builder” Pieces of the lithosphere that move around Each plate has a name Fit together like jigsaw puzzles Float on top of mantle similar to ice cubes in a bowl of water

Alfred Wegener Born in Berlin 1880 Died in Greenland 1930 In 1915 he argued that there had once been a huge super continent, which he named 'Pangaea', made up of all the land masses on the planet. He chose the name Pangaea because it means 'all earth'.

Continental Drift Theory Alfred Wegener’s theory Continents were once a single land mass that drifted apart. Fossils of the same plants and animals are found on different continents 245 Million years ago 1st split Split again – Laurasia & Gondwana 180 million years ago http://members.enchantedlearning.com/subjects/astronomy/planets/earth/Continents.shtml

Evidence of Pangea

Sea Floor Spreading

Mid-Ocean Ridge: topographical section

Sea Floor Spreading Mid Ocean Ridges – underwater mountain chains that run through the Earth’s Basins Magma rises to the surface and solidifies and new crust forms Older Crust is pushed farther away from the ridge

Sea Floor Spreading

Subduction Oceanic crust is pushed down into the mantle.

How Plates Move http://pubs.usgs.gov/gip/dynamic/unanswered.html

Notes for Plate Tectonics – Part 1 Set up your notes page like this one. 2.5” column on the left. This space is for main ideas or questions. 6” column on the right. This space is for notes and details. 2” space at the bottom. This space is for summarizing the notes.

What are the layers of the Earth? Crust: outermost layer; 5 – 100 km thick. Broken into many plates. Mantle: layer between the crust and the core. Most of the Earth’s mass. Asthenosphere layer is flowing rock. Core: center of the Earth. Pieces of the Earth’s crust that move around over the flowing mantle. Plates fit together like a puzzle. The moving plates of the lithosphere provide evidence that the continents were once a single mass and have moved over time. What are Tectonic Plates? How do tectonic plates relate to Continental Drift Theory?

How do the plates move around? Sea Floor Spreading: magma pushes up through the crust forming underwater mountain chains – Mid Ocean Ridges. Subduction: in some areas convergent boundaries push some of the crust into the mantle, forming ocean trenches. Convection Currents: the flowing mantle circulates due to differences in density.

Different Types of Boundaries http://pubs.usgs.gov/gip/dynamic/understanding.html

Divergent Boundary – Arabian and African Plates Arabian Plate Red Sea African Plate

Divergent Boundary – Iceland http://pubs.usgs.gov/gip/dynamic/understanding.html

Divergent Boundary - Oceanic http://www.geology.com

Divergent Boundary - Continental http://www.geology.com

Convergent Boundary – Indian and Eurasian Plates Indian Plate

Convergent Boundary – Oceanic & Continental http://pubs.usgs.gov/gip/dynamic/understanding.html & http://www.geology.com

Convergent Boundary – Oceanic & Oceanic Note – plates are reversed http://pubs.usgs.gov/gip/dynamic/understanding.html & http://www.geology.com

Convergent Boundaries - Continental http://pubs.usgs.gov/gip/dynamic/understanding.html & http://www.geology.com

Transform Boundary – San Andreas Fault www.geology.com

Plate Tectonics Notes Part 2 – Plate Boundaries What happens when the tectonic plates move? Tectonic plates have boundaries between them. Plate boundaries form mountains, trenches and valleys. Earthquakes and volcanoes are also caused by plate boundaries.

Overview of Divergent Boundaries Oceanic divergent boundary Continental divergent boundary Divergent Boundaries: Plates pull apart.

Convergent Boundaries: Plates push together. Convergent boundary: oceanic and continental. Convergent boundary: oceanic and oceanic. Convergent boundary: continental

Transform Boundaries: Plates slide together horizontally. Also called a strike-slip boundary.

The End