Chapter 4 Tectonic Plates Flashcards
Accretionary prism
Forms in a convergent/ subduction zone. As subducting plate goes down the sediment from it gets pushed up.
Volcanic arc
Develops behind a accretionary prism .
East African Rift Valley
Divergent boundary. If continues one day Africa continent will be in separated.
Thomas Kuhn
“Scientific Revolution”
1960s, historian of science. Says scientists base there interpretation of the natural world by reasoning and their experiences.
Plate tectonics. Who made previous research.
Tectonics theory evolved in the 1960s.
Wegner(1915) evidence supporting continental drift.
Hess/dietz (1960) the sea-floor spreading hypothesis.
Geologists adopted…
Tectonics theory by 1968, evidence was overwhelming.
Harry Hess and Robert Dietz’s
Proposal that sea floor is spreading
Lithosphere
Consists of the crust plus the uppermost (coolest) part of upper mantle. Acts elastically, bends, flexes and sometimes breaks. Floats on the asthenosphere.
Asthenosphere
Warmer mantle that can flow when acted in by force.
Continental and oceanic lithosphere.
Differ in thickness. Continental =150km
Old Oceanic =100km
New oceanic crust = 7 to 10 km
Principle of buoyancy
Floating solids displace water equal to their mass.
- and iceberg “sinks” until the mass of water it displaces is equal to the total mass of the iceberg.
- concept applies to lithospheric plates.
How many plates make up lithosphere?
20 tectonic plates. Plates move continuously at a rate of 1-15cm/yr.
They come in a variety of sizes and shapes. They can change shape and size throughout their history.
-
Plate Boundaries
Where tectonics plates meet.
- identified by concentration of earthquakes.
- associated with many other dynamic phenomena.
- plates interiors are almost earthquake free.
-
Continental Margins
Where land meets ocean. Margin near plate boundaries are active.
- margins far from plate boundaries are passive
-
Divergent boundary
Tectonic plates move apart.
- lithosphere thickens away from the ridge axis
- aka spreading boundary, mid-ocean ridge, ridge
Convergent boundary
Tectonic plates that move together. Called subduction. Plate consumption. Aka convergent margin, subduction zone, trench
Transform boundary
Tectonic plates slide sideways.
Plate material is neither created not destroyed. Aka transform fault. Slip parallels the earths surface. San Andrés fault last time was districting was in 1906.
Triple junctions
Where tree plate boundaries intersect at a point. Ex: southwest Indian Ocean ridge intersects two arms of mid-Indian ocean ridge (African, Antarctica and Australian plates)
These plate boundaries can be ridges and transforms
Plate-boundary volcanoes
Subaerial volcanoes (above sea level) at volcanic arcs that border trenches. Most submarine volcanoes (underwater) lie given along mid-ocean ridges. Formed as a consequence of movement along boundary.
Hot spring
Volcanoes that are located in the interiors of plates away from the boundaries but some are straddle mid-ocean ridges
Pg 104 deep plum mantle model for hot spots good to write in the term paper.
Canadian geologist . End of pg 104 Yellowstone national park is brought up.
Relative plate velocity
Comparing the movement of two plates.
Absolute plate velocity
Describe movement of two plates relative to a fixed point in the mantle
Global Positioning System (gps)
Geologists use an array of GPS receivers to monitor plate displacements of millimeters per year.
Volcano
A vent where molten rock comes out of earth.
