Global Distribution of Tectonic Hazards Flashcards
What are hotspots?
Small areas of crust with unusually high heat, far away from any plate boundaries.
Where do oceanic hotspots occur?
Where plumes of magma rise from asthenosphere, magma may either escape in an eruption or build up over time into a volcanic island.
How are the Hawaiian islands an example of a hotspot?
They are formed by a stable hotspot. As the pale has moved, the island chain keeps getting extended north-west, forming a chain of extinct underwater volcanoes called seamounts.
What is the volcano currently eruption in Hawaii?
Loiti is erupting 35km south-east of Hawaii. Explosions are common as Kilaneu, Mauna Kea and Mauna Loa are taller than Mt Everest.
How is Yellowstone an example of a hotspot?
There is a continental hotspot below Yellowstone, formed by a probable explosive eruption of a rhytholitic super volcano. 2.1 million years ago an eruption ejected 6000 times more gas and lava than Mt St Helens.
How many earthquakes have been recorded globally since 2010?
30,000
What is the standard distribution of earthquakes?
Not random - closely follow plate boundaries
What are the 4 plate settings which categorise seismic activity?
Diverging, Converging, Collision and Transform.
What are seismic activities that result from diverging boundaries?
Mostly shallow and result from tensional faults and shaking during volcanic activity. Many are submarine and post little threat to people
What are seismic activities that result from converging boundaries?
Where oceanic crust is subjected or 2 plates collide. Subject to high-magnitude earthquakes and are areas of major hazards. Tsunamis can form from these also.
What are seismic activities that result from collision boundaries?
Continental crusts collide to produce mountain ranges. Shallow earthquakes in a broad zone - high risk hazards.
What are seismic activities that result from transform boundaries?
Shallow, high magnitude earthquakes. San Andreas Fault.
How many earthquakes are intra-plate, how does this occur and what is an example?
15%, caused by stresses to crustal rocks, resulting in isostatic recoil which is unpredictable. Tangsten, China in 1976 had 240,000 deaths due to this.
What is a quasi- natural earthquake?
Killani - India had an earthquake that resulted from the weight water in a new reservoir which lubricated a fault line and allowed it to slip.
Fracking is also an issue, there was an earthquake in North Lancaster in 1996 - fracking suspended in UK in 2015.
