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Is Pinatubo on a hot spot?
No. Mount Pinatubo is on a subuction zone.
How did the Sierra Nevada Range form?
Where tectonic plates collide, the intervening crust can be folded or pushed up to form mountains. In the case of the Sierra Nevada, an ancient collision forced magma from an oceanic plate beneath the western part of North America. After millions of years, erosion and glaciation has exposed these underground rocks, or plutons, which form the bases of the mountains of the range.
Is mt Pinatubo formed at a hot spot?
No. A hot spot volcano forms in the middle of a plate, for reasons nobody is sure of. Mount. Pinatubo is formed due to the destructive plate boundary between the Pacific (oceanic ) and the Eurasian (continental) plates. +++ A hot spot volcano is also called an 'intra-plate volcano'. One theory if that it forms over a rising convection-plume within the Mantle, but the existence of such relatively narrow columns of slightly less dense rock is a matter of some debate, being very hard to prove convincingly. Structures deep within the planet can only be detected by analysing many seismographs from around the world, and my own thought is that the acoustic properties of a mantle-plume may mean very limited effects on seismic waves, making it hard to "see" against the surrounding Mantle. ' Hawaii is the classic example of such a volcano, and it has left a trail across part of the Pacific floor as the plate itself has drifted over the hot spot. ' Volcanoes also form on constructive-plate boundaries, and tend to be more benign than the destructive-boundary cousins. Example - Iceland.
What 3 factors determine the amount of damage created by an earthquake?
1. Distance from the epicenter/focus 2. Duration of Shaking 3. Magnitude 4. Ground material These all lead to the types of earthquakes (Subduction Zone EQs, Deep EQs and Shallow Crustal EQs), which leads to plate tectonics, which then leads to plate boundaries. Subduction Zone EQs Deep EQs Shallow Crustal Faults Subduction Earthquakes - Juan de Fuca plate is sliding underneath North American plate -friction - What happens with the subuction zone breaks? -As the interface area moves, the strain in the overlying plate is released. Areas of the overlying plate are uplifted and other parts subside. We call this rebound (land can either go up or down). Summary: -Where? at the interface of the Juan de Fuca and North American plate -Why? locking-bulging, ^^^ slipping-rebounding mechanism -How frequent? every 300-500 years -How strong? 8.5-9M -Area potentially effects? 1-4 minutes Deep earthquakes in subducting slab (i.e. Nisqually earthquake) -Hot on the outside, ice cold on the inside (i.e. deep fried ice cream). -center of plate is still cold (outer is hot), earthquakes are in the center due to coldness which leads leads to brittle breakage. Summary Deep earthquakes -Where? at depths of 35-60 km in the Juan de Fuca subducting plate -Why? Phase changes in the subducting slab ^^^ -How strong? 6-7.5 M (moderate) -How frequent? one ever 30 years avr. -Shaking effects? 14-30 seconds -Area affected? localized in area above subducting slab -potential damage? significant to extensive (i.e. Seattle Fault, Tacoma Fault and Urban Earthquakes - many local faults in the Puget Sound Region) -Where? Shallow in the North American plate (includes the Puget Sound Region) -Why? Regional compressional stress applied on pre-existing crustal faults -How strong? up to 7.5M -How frequent? uncertain... -Damage? localized but extensive
