Tectonic plate movements that have been documented by scientists led to the Theory of Plate Tectonics. The Earth's outer shell is the crust and it is broken into large and small crustal plates.
The plates are moving around the Earth's surface at different speeds. The Atlantic Ocean is increasing in size about the speed your fingernails grow along the Mid Atlantic Ridge. In the Pacific Ocean plates are separating at the East Pacific Rise about the speed your hair grows.
Crustal plates move apart, come together and slip past each other horizontally. Each of these plate movements creates a different type of plate boundary.
Divergent plate boundaries are places where two plates are moving apart. In the North Atlantic Ocean is the Mid-Atlantic Ridge that has formed where the North American and Eurasian Plates are separating.
Where diverging plates are separating fissures open on the ocean floor allowing molten rock from the mantle to flow out forming pillow basalt. Molten rock seals the fissures after an eruption creating new oceanic crust.
There are two types of convergent boundaries. When two continental plates collide they form a collision boundary and great mountain chains form between the two continental crusts. The Himalayan Mountains are increasing in height as the Eurasian and Indian Plates collide.
Subduction zones form when an oceanic plate converges with a continental plate or another oceanic plate. The heavier and denser oceanic plate is bent and forced downward into the upper mantle where the rocks are recycled. On the continental side of a subduction zone great volcanoes rise like Mount Pinatubo, Mount Fuji and Mount Rainier.
Transform boundaries form when two plates move past each other horizontally. The San Andreas Fault is a world famous transform fault. The master fault runs down the state of California from the Mendocino Triangle in the north south to the East Pacific Rise off the coast of Mexico. It separates the Pacific Plate from the North American Plate. The Pacific Plate is moving northward relative to the North American Plate.
Transform faults are also found on ocean floors where the curvature of the Earth causes rift valleys to be offset. The transform faults connect rift valleys as the plates separate.
Crustal Plates Find out how continental crust and oceanic crust forms on our planet.
The Earths Mantle Find out about the Earths mantle that contains 84% of the Earth's mass.
Earths Interior Find out about layers that have formed inside out planet and how they were discovered.
Alaska Northern Lights Learn how and why the Northern Lights light up the sky in the Northern Hemisphere.
Earths Crust Find out where the newest crust on our planet forms and which type of crust is the oldest.
Plate Movements Do you know what are divergent plate boundaries, convergent boundaries and transform faults. Find out on this page.
Planet Earth Find out about the different layers that make up planet earth from the core to outer space.
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