_02_Tectonics_Cascades

_02_Tectonics_Cascades - GEOLOGY 20 - LECTURE 2 PLATE...

Info iconThis preview shows pages 1–3. Sign up to view the full content.

View Full Document Right Arrow Icon
1 GEOLOGY 20 - LECTURE 2 PLATE TECTONICS & THE CASCADES (Ch. 1, 5 in Harden) Plate Tectonics The global pattern of earthquake locations and volcano distribution exhibits linear trends, with earthquakes and volcanoes commonly located along the edges of continents or strung out along linear trends down the middle of ocean basins. The locations of earthquakes and volcanoes coincide with the margins of plates - large, tabular slabs of the Earth’s outer surface that are in constant slow motion. Where the plates grind against each other is where geology happens. Due to the continual slow motion of plates, the geography of the Earth is ever-changing. Plate tectonics - the continual motion, creation, and destruction of tabular outer slabs of the planet’s active surface. plate ” refers to the shape of the moving sections of Earth’s outer surface. ~ 12 major plates plus several smaller plates; plates typically include both continents and parts of oceans (less commonly, plates may be composed solely of continental rock or solely of oceanic rock). tectonics refers to large scale movement and deformation of Earth’s outer surface (crust plus upper mantle) How thick are tectonic plates? The Earth is composed of an interior core, surrounding mantle and outermost crust. Earth’s radius is about 6300 km. Tectonic plates are only ~100-250 km (60-150 miles) thick, and consist of the uppermost mantle and crust (which together form a layer called the lithosphere). lithosphere = crust and upper mantle down to about 100 to 250 km beneath Earth’s surface – tectonic plates are lithospheric - lithosphere beneath continents is thicker (~150-250 km) than lithosphere beneath oceans (~100 km) - lithosphere is a “cool and strong” layer of rock that behaves rigidly (it bends, flexes, and breaks, but does not flow easily)
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
2 asthenosphere = upper mantle down to ~ 400 km - boundary between lithosphere and asthenosphere defined by a temperature of ~1280°C, the temperature at which rock (at high pressures) begins to partially melt and slowly flow when acted upon by a force - asthenosphere is a “hot, weak, semi-plastic” layer of rock that will slowly flow Plate tectonics involves the movement of cool, strong, stiff lithospheric plates over the hot, weak, semi-plastic asthenosphere. What is the energy source for the movement of plates?
Background image of page 2
Image of page 3
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 03/10/2012 for the course GEL 20 taught by Professor Osleger during the Winter '08 term at UC Davis.

Page1 / 5

_02_Tectonics_Cascades - GEOLOGY 20 - LECTURE 2 PLATE...

This preview shows document pages 1 - 3. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online