Classification of Igneous Rocks: Intrusive vs. Extrusive

The video tutorial explains the classification of igneous rocks, focusing on the differences between extrusive (volcanic) and intrusive (plutonic) rocks. Volcanic rocks are classified based on silica content, while plutonic rocks are named according to their mineral composition. The tutorial also discusses the types of igneous rocks found at the Earth's surface, influenced by geological settings like mid-ocean ridges and subduction zones.

What is the primary difference between extrusive and intrusive igneous rocks?

• Extrusive rocks cool quickly at the surface, while intrusive rocks cool slowly at depth.

• Extrusive rocks form at depth, while intrusive rocks form at the surface.

• Extrusive rocks cool slowly, while intrusive rocks cool quickly.

• Extrusive rocks are always larger than intrusive rocks.

Which volcanic rock has a silica content greater than 69%?

• Basalt

• Rhyolite

• Andesite

• Dacite

What is the main mineral composition of basalt?

• Plagioclase and amphibole

• Amphibole and mica

• Olivine and pyroxene

• Quartz and feldspar

How are plutonic igneous rocks named?

• Based on their three most abundant minerals

• Based on their cooling rate

• Based on their location of formation

• Based on their color

Which rock is the plutonic equivalent of basalt?

• Gabbro

• Diorite

• Peridotite

• Granite

Where is basaltic lava most commonly found?

• At the poles

• At mid-ocean ridges

• In desert regions

• In continental interiors

What type of magma is typically produced at subduction zones?

• Ultramafic

• Rhyolitic

• Andesitic

• Basaltic