Plate Tectonics. Earth’s Layers The Earth's rocky outer crust solidified billions of years ago,...
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Transcript of Plate Tectonics. Earth’s Layers The Earth's rocky outer crust solidified billions of years ago,...
Plate Tectonics
Earth’s LayersThe Earth's rocky outer crust solidified billions of years ago, soon after the Earth formed.
This crust is not a solid shell; it is broken up into huge, thick plates that drift atop the soft, underlying mantle.
The Crust
• Outermost layer• 5 – 100 km thick• The solid part of earth is called the
lithosphere
The Mantle• Layer of Earth
between the crust and the core
• Contains most of the Earth’s mass
• Has more magnesium and less aluminum and silicon than the crust
• Is denser than the crust
• The liquid part of the Earth is called the asthenosphere
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
• Gravity draws everything to the core.
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
Plate Tectonics
• The plates move around on the asthenosphere
• The theory that the Earth’s crust is broken into sections.
• Causes earthquakes, volcanoes, trenches and mountains on Earth
Continental Drift• Pangaea• Alfred Wegener suggested
that all the continents were once joined together in the past and broke apart about 200 million years ago. He thought this because of the apparent way that the continents fit together like pieces of a puzzle. The large landmass was called Pangaea.
Continental DriftAlfred Wegener 1900’sContinents were once a single land mass that drifted apart.
Fossils of the same plants and animals are found on different continents
Called this supercontinent Pangea, Greek for “all Earth”
245 Million years ago
Split again – Laurasia & Gondwana 180 million years ago
Evidence of Pangea
Evidence of Pangaea
• Fossils• Rock formations• Continent shape
Sea Floor Spreading
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 pushedfarther away from the ridge
How Plates Move
http://pubs.usgs.gov/gip/dynamic/unanswered.html
Different Types of Boundaries
http://pubs.usgs.gov/gip/dynamic/understanding.html
Divergent Plate Boundaries
Plates move apart
Ex: Mid Ocean Ridges, Continential rifts
Divergent Boundary – Arabian and African Plates
Divergent Boundary Iceland
African Rift
Convergent Boundaries
Plates collide
EX: Mountains, trenches, and island arcs
Convergent Boundaries - Continental
http://pubs.usgs.gov/gip/dynamic/understanding.html & http://www.geology.com
Convergent Boundary – Indian and Eurasian Plates
Subduction
When an ocean plate sinks beneath a continental plate.
EX: Trenches, volcanoes
Convergent Boundary – Oceanic & Continental
http://pubs.usgs.gov/gip/dynamic/understanding.html & http://www.geology.com
Convergent Boundary – Oceanic & Oceanic
http://pubs.usgs.gov/gip/dynamic/understanding.html & http://www.geology.com
Island Arcs
• Aleutian Islands • Northeastern Japan arc
• Japan and Ryukyu Islands
• Mariana Islands • Philippines
Transform boundaries
Plates slide past each other.
EX: San Andreas Fault, earthquakes are common on
transform boundaries.
Transform Boundary – San Andreas Fault
www.geology.com
Review
• Name the 3 main layers of the Earth• What is a tectonic plate?• What was Pangea?• What is Sea-Floor spreading?• Name the three different types of plate
boundaries and one location on Earth for each one
Divergent boundaries
Convergent boundaries
Transform boundaries
