Why are the crystals of intrusive igneous rock typically larger than those of extrusive igenous rock?
a. because the magma cools very quickly
b. because the magma cools much slower
c. because of a higher water content in the magma
d. because the temperatures of the magma are much lower

Why is the huronian supergroup rock formation particularly interesting to scientists? because it looks like a cross-section of a giant, stone encyclopedia because it formed during the period when oxygen began to accumulate in the atmosphere because it contains unusually large amounts of oxygen and sulfur because it dramatically altered the planet's development when it first formed