Video Transcript
Fill in the blanks. Igneous blank rocks take a blank
time to cool and therefore produce blank crystals. (A) Volcanic, longer,
larger-sized. (B) Plutonic, longer,
larger-sized. (C) Plutonic, longer,
smaller-sized. (D) Plutonic, shorter,
smaller-sized. (E) Volcanic, longer,
smaller-sized.
This question is about igneous
rocks. Igneous rocks are rocks formed from
the cooling and solidification of hot molten material found below the Earth’s
crust. When this hot molten material is
found below the surface of the Earth, it’s known as magma. But when magma flows to the surface
of the Earth, it’s then referred to as lava. Magma and lava are under different
conditions and therefore produce different types of igneous rocks. To answer the question, we need to
correctly match the type of igneous rock to the length of time it takes to cool and
the size of the crystals it contains.
Magma has a high ambient
temperature and therefore cools slowly. The rocks formed when magma cools
consist of large-sized crystals. This is because the slow cooling of
magma allows time for the different substances in the rock to arrange themselves,
causing larger crystals to grow. We call the type of igneous rock
formed when magma cools slowly plutonic rock.
Lava above the surface of the Earth
cools much more quickly than magma. Because lava cools quickly, there
isn’t sufficient time for large crystals to grow. So these rocks contain small-sized
crystals. We call the type of igneous rock
that forms when lava cools quickly volcanic rock.
So igneous volcanic rocks take a
shorter time to cool and therefore produce smaller-sized crystals, while igneous
plutonic rocks take a longer time to cool and therefore produce larger-sized
crystals.
Looking at the answer choices, we
can see that the answer choice that correctly matches the type of igneous rock to
the length of time it takes to cool and the size of the crystals it produces is
answer choice (B). So answer choice (B), plutonic,
longer, larger-sized, is the correct answer.
If we fill in the blanks with these
words, we get the statement “Igneous plutonic rocks take a longer time to cool and
therefore produce larger-sized crystals.”
