# How are earthquakes formed at continental-continental boundaries?

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#1
I understand that at other destructive plate boundaries the oceanic plate is subducted into the Benioff zone so earthquakes occur. But how are they formed when two continental plates converge?

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7 years ago
#2
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7 years ago
#3
Hi,

When two continental plates converge neither is subducted as both have the same density of around 2.7g/cm^3 so as you rightly said, there is no Wadati-Benioff zone (the pattern of earthquake foci that mark the path of the descending plate). However, don't forget that when two things converge, there's an awful lot of compressional force and pressures. So think of it like this, if neither plate is being subducted, where is all the pressure going?

What happens when you get two rubbers and push them into each other? Do they move upwards or downwards? And when the pressure force exceeds the frictional force, is the movement sudden or slow?

Remember that an earthquake is caused by sudden movement of rock units (in this case two continental crusts) which releases energy in the form of seismic waves).

Hope this helps,

TS18
0
7 years ago
#4
(Original post by TheStudent18)
Hi,

When two continental plates converge neither is subducted as both have the same density of around 2.7g/cm^3 so as you rightly said, there is no Wadati-Benioff zone (the pattern of earthquake foci that mark the path of the descending plate). However, don't forget that when two things converge, there's an awful lot of compressional force and pressures. So think of it like this, if neither plate is being subducted, where is all the pressure going?

What happens when you get two rubbers and push them into each other? Do they move upwards or downwards? And when the pressure force exceeds the frictional force, is the movement sudden or slow?

Remember that an earthquake is caused by sudden movement of rock units (in this case two continental crusts) which releases energy in the form of seismic waves).

Hope this helps,

TS18
What determines the direction of the movement of the plates? Just a curious AS level geog student.
0
7 years ago
#5
(Original post by Hody421)
What determines the direction of the movement of the plates? Just a curious AS level geog student.
Hi,

There's a part of the mantle called the asthenosphere that is located beneath the lithosphere. The lithosphere consists of the upper part of the mantle (which is solid) and the crust. The asthenosphere however, is rheid material (semi-molten). There are convection currents that circulate in the asthenosphere and its these convection currents that essentially drag the plates either towards, away or parallel to each other.

It really is quite simple when you think about it (at this level at least!), but this is the basis of plate tectonics.
0
7 years ago
#6
(Original post by TheStudent18)
Hi,

There's a part of the mantle called the asthenosphere that is located beneath the lithosphere. The lithosphere consists of the upper part of the mantle (which is solid) and the crust. The asthenosphere however, is rheid material (semi-molten). There are convection currents that circulate in the asthenosphere and its these convection currents that essentially drag the plates either towards, away or parallel to each other.

It really is quite simple when you think about it (at this level at least!), but this is the basis of plate tectonics.
Thanks, one more question though. Are there any factors other than better emergency systems/infrastructure that makes MEDCs less susceptible to casualties?
0
7 years ago
#7
(Original post by Hody421)
Thanks, one more question though. Are there any factors other than better emergency systems/infrastructure that makes MEDCs less susceptible to casualties?
No problem. And yes, think about education of the people. For example, people in MEDCs tend to have higher literacy levels opposed to those in LEDCs. Think about Tacloban, Philippines during the Typhoon Haiyan event. One man said to a reporter something along the lines of 'If we knew what a storm surge was, we would have been able to prepare for it', which would have most likely reduced the death toll of the event. Education is vital and often is the difference between life and death in natural disasters as people will be able to prepare for the event.

By emergency systems I assume you mean evacuation plans, training for emergency services etc.? Going back to the education idea, Italy has a Civil Protection Department in which volunteers are educated on how to rescue people during natural disasters as Italy lies close to the Eurasian and African converging plate boundary and also has the active north-south fault line running through its centre along the Apennines.

Also think of the idea that MEDCs have more money to invest in seismometers etc. and of course seismologists, but I assume you meant things like this under emergency systems.
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