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Are there any geologists on here?!


Brownie Guider
This is going to sound a random question, but is anyone a geologist?
I am looking for a simple explanation of why oceanic and continental crust have different mineral compositions, but do not seem to find anything on google! I ideally want something a few sentences long (because anything longer will not be read!)

I need it because I am trying to set up an earthcache (geology based geocache, where you have to make observations in the field) and I am getting people to look at different types of igneous rock, which have different mineral compositions, due to some of the rocks being found in continental crust and the other one in oceanic crust.

A lot of people reading the earthcache page will not be geologists, and it is recommended that it is written at age 14 reading level.

Thank you!


Guide Guider
Sister has given me the following response:

Well i think something like oceanic is sedimentary whereas continental is volcanic. Even if the continental is recycled oceanic, it's spewed out all different. Ocean = dead sea stuff, continental = volcano vomit


Veteran (100+ posts)
I am a geologist this might help
Continental crust is less dense than oceanic and this is due to the rocks that make it up. Rocks have different minerals in them like cakes have different ingredients.
The oceanic crusts (those that are formed mainly under water where the plates part and magma from deep in the earth comes up to form new crust. The oceanic rock is is basaltic in composition (low amount of silica). They don't come from violent volcanic eruptions.

Continental crust is mainly recycled continental crust from nearer the surface which is mainly rocks that are granitic - rich in silica rich. If more water goes down with the old crust then the volcanoes that make the new crust then the more violent the volcano is.

hope this helps