The rocks exposed in Boulder Canyon are almost all igneous. The texture of these

Question

The rocks exposed in Boulder Canyon are almost all igneous. The texture of these igneous rocks is phaneritic. By recognizing this texture you can tell the following about the geologic history of Boulder Canyon:

Question 4 options:

The rocks cooled so quickly that crystals were unable to form

The rocks of Boulder Canyon must form a dike, because if they formed a sill the texture would be aphanitic instead

An explosive volcanic eruption formed the rocks of Boulder Canyon, meaning that the rocks were likely formed in a caldera

The silica content of the Boulder Canyon rocks is low, meaning that the canyon is composed of continental crust

The rocks of Boulder Canyon lay far beneath the surface when they formed, meaning that a major episode of erosion occurred since then

a)

The rocks cooled so quickly that crystals were unable to form

b)

The rocks of Boulder Canyon must form a dike, because if they formed a sill the texture would be aphanitic instead

c)

An explosive volcanic eruption formed the rocks of Boulder Canyon, meaning that the rocks were likely formed in a caldera

d)

The silica content of the Boulder Canyon rocks is low, meaning that the canyon is composed of continental crust

e)

The rocks of Boulder Canyon lay far beneath the surface when they formed, meaning that a major episode of erosion occurred since then

Explanation / Answer

solution:-

The rocks of Boulder Canyon lay far beneath the surface when they formed, meaning that a major episode of erosion occurred since then.

Phaneritic texture of igneous rocks describes the rock with large crystals. These are formed below the earths surface and are also called Plutonic rocks. Since they are formed below the surface they take a larger time to cool and hence larger crystals are formed. So, according to me the option E is the most suitable ans for the above question. As they show phaneritic texture they must have been formed below the surface of the earth and after a major period of erosion have come to the surface.

e)

The rocks of Boulder Canyon lay far beneath the surface when they formed, meaning that a major episode of erosion occurred since then.

Phaneritic texture of igneous rocks describes the rock with large crystals. These are formed below the earths surface and are also called Plutonic rocks. Since they are formed below the surface they take a larger time to cool and hence larger crystals are formed. So, according to me the option E is the most suitable ans for the above question. As they show phaneritic texture they must have been formed below the surface of the earth and after a major period of erosion have come to the surface.

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