Why is it unlikely to find earthquakes at depths greater then 300km? (something to do with the athenosphere)
According to the principle of isostasy, what will happen to the elevation of a mountain range in the early stages of erosion?
Why are continents unlikely to be destroyed by the process of subduction?
Thanks alot
I think a better subject title for this would be "geology."
Since this is not my area of expertise, I searched Google under the key words "asthenosphere earthquake" to get these possible sources:
http://en.wikipedia.org/wiki/Asthenosphere
http://www.blackwell-synergy.com/doi/abs/10.1111/j.1365-246X.2006.02815.x?journalCode=gji
http://www.earthquakecountry.info/10.5/MajorMovieMisconceptions/
http://www.bartleby.com/65/as/asthenos.html
http://www.globalchange.umich.edu/globalchange1/current/lectures/evolving_earth/evolving_earth.html
Under "isostasy mountain erosion" I found:
http://en.wikipedia.org/wiki/Isostasy
http://findarticles.com/p/articles/mi_m0GDX/is_3_76/ai_75434343
http://gpc.edu/~pgore/geology/geo101/mountain.htm
(Broken Link Removed)
Under "subduction continents" I found:
http://www.enchantedlearning.com/subjects/astronomy/planets/earth/Continents.shtml
(Broken Link Removed)
http://en.wikipedia.org/wiki/Plate_tectonics
http://en.wikipedia.org/wiki/Continental_collision
http://www.platetectonics.com/book/page_12.asp
In the future, you can do your own searches using appropriate key words.
I hope this helps. Thanks for asking.
Why is it unlikely to find earthquakes at depths greater than 300km?
The main reason why earthquakes are unlikely to occur at depths greater than 300km is because of the nature of the asthenosphere. The asthenosphere is a layer of the Earth's mantle located below the lithosphere. It is semi-fluid and behaves like a plastic material, which allows the tectonic plates to move and slide on top of it.
Earthquakes occur when there is a sudden release of energy along a fault line, which is a fracture in the Earth's crust. This release of energy generates seismic waves that can be felt at the Earth's surface.
However, at depths greater than 300km, the pressures and temperatures are extremely high, causing the rocks in the asthenosphere to become ductile and deform slowly rather than fracture. This means that there is less likelihood of a sudden release of energy and therefore fewer earthquakes at these depths.
According to the principle of isostasy, what will happen to the elevation of a mountain range in the early stages of erosion?
The principle of isostasy states that the Earth's crust is in a state of balance and will adjust its elevation in response to changes in the load placed upon it. When a mountain range is formed through tectonic forces, the crust is uplifted and forms a higher elevation.
During the early stages of erosion, the external forces of wind and water start to wear away at the mountain range. As material is eroded and removed from the mountain, the load on the underlying crust decreases. In response, the crust will start to slowly rise or rebound, compensating for the loss of material.
This means that in the early stages of erosion, the elevation of a mountain range will actually increase, as the crust tries to maintain its state of balance. However, over time, as erosion continues, the rate of uplift will decrease and eventually the mountain range will erode down to a lower elevation.
Why are continents unlikely to be destroyed by the process of subduction?
The process of subduction occurs when one tectonic plate is forced under another plate and sinks into the Earth's mantle. This typically happens at convergent plate boundaries, where two plates are moving towards each other.
Continents are composed of lighter and less dense rocks compared to the oceanic crust. When a convergent boundary occurs between an oceanic plate and a continental plate, the denser oceanic plate is subducted beneath the lighter continental plate.
However, because of their lower density, continents are much less likely to be completely subducted and destroyed. Instead, they tend to resist subduction and can cause the subducting oceanic plate to buckle and form mountain ranges along the continental margin.
This resistance to subduction is due to the buoyancy and thickness of the continental crust. The continental crust is typically thicker and less dense than the oceanic crust, making it harder for the oceanic crust to sink beneath it.
Additionally, continents contain large amounts of granitic rocks, which are less dense and more buoyant than the basaltic rocks found in the oceanic crust. This buoyancy further prevents the continents from being easily destroyed by the process of subduction.
In summary, due to their buoyancy, thickness, and composition, continents are unlikely to be completely destroyed by the process of subduction. They are more likely to resist subduction and can influence the formation of mountain ranges instead.