Circle the letter of cach sentence that is true about silica. a. It is formed from oxygen and nitrogen. b. It makes magma thicker, .
C. It is rarcly found in the crust,
d. It produces light-colored lava.

The correct answer choices are B and D.

Explanation:

A volcanic eruption happens when magma reaches the surface of the earth.  Depending on the amount of gas and the silica content of the magma, the lava and the type of eruption can vary.  Silica, which forms from the elements silicon and oxygen, makes the lava thicker and less runny. When lava is thick, the volcanic eruption tends to be more explosive.  The amount of silica also changes the color and density of the lava, which then makes different kinds of igneous rocks.  As the gas content of the lava goes up, the eruption becomes more explosive.