Plate Tectonics

Earth’s Layers The 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 Drift Alfred Wegener 1900’s Continents 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 pushed farther 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 Arabian Plate Red Sea African Plate

Divergent Boundary Iceland

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

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

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 Indian Plate

Subduction When an ocean plate sinks beneath a continental plate 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 Note – plates are reversed 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 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

Convergent boundaries Transform boundaries Divergent boundaries