Geology (cont. 3)


From other locations, more lava erupted and cooled into greenish-gray andesite, which got its name from similar rock found in the Andes Mountains. Not all of the melted rock came out onto the surface as lava flows. Some was trapped and cooled under miles of rock and sediment. It became granodiorite, a rock like granite but lacking one of the essential minerals of true granite. Other related rocks cooled under the surface also. We will call them “granitics” to mean rock cooled underground (intrusive igneous rock). These masses of rock would become the Southern California Batholith. Look for cobbles of all of these types of rocks on the North County beaches.


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