earthquakes 2

earthquakes 2 - Earthquakes 9-4-6 Narrow belts are in the...

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Earthquakes 9-4-6. Narrow belts are in the middle of the ocean and create smaller earthquakes Dipping zones of earthquakes off the coast that start in trenches are wadati-benioff zones. - edges of major plates are where the biggest earthquakes are. - The earthquake belts perfectly delineate the edges of these plates 3 basic points 1. earthquake belts mark edges of dozens large, thin, rigid, “tectonic plates” that cover the earth. - almost all large earthquakes occur at these edges - plates are about 100 km thick (oceanic plates), 200-500 km thick continental plates - made up of lithosphere and these lithospheric plates move relative to one another on top of aesthenosphere – a “slushy” layer. 2. almost (98%) all tectonic activity (mountain building and related activities. Tecktos = Greek “builder” also used in architecture) earthquakes, volcanoes, occur at boundaries of these plates. - 3. three types of plate boundaries. - divergent – plates pull away from each other. 1. mid ocean mountain ranges are sites where new oceanic lithosphere is created. As plates move away from each other, rising magma emerge onto the surface or forms oceanic crusts. As plates diverge, lithosphere thickens on top of aesthenosphere. Known as spreading centers or mid-ocean ridges. Abyssal plain is 5km, which is formed by the lithosphere. Magma comes to surface, lava that flows out is known as basalt – runny, fluid. Basalt volcanoes don’t explode or erupt. They’re huge broad gently sloping (low slope) shield volcanoes - hawaii. 1st example: Mid-atlantic ridge. North American plate and Eurasian plate moves apart from each other because of these divergent plates. The one point where midatlantic ridge rises above the ocean is Iceland. Iceland is the site of a “ploom”: and is splitting apart due to the divergent plates. Sea water go where the plates splits, becomes steam, goes back up, hits cold ocean
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This note was uploaded on 01/23/2009 for the course GEOL 240Lxg taught by Professor 12:30-01:50pm during the Fall '07 term at USC.

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earthquakes 2 - Earthquakes 9-4-6 Narrow belts are in the...

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