Understanding Igneous Rocks

What is the primary process that leads to the formation of the Earth's crust?

• Partial melting of mantle rock

• Weathering of rocks

• Metamorphic transformation

• Sedimentation

Which type of igneous rock forms when magma solidifies beneath the Earth's surface?

• Extrusive

• Sedimentary

• Intrusive

• Metamorphic

What is a pluton in geological terms?

• A type of metamorphic rock

• A type of sedimentary rock

• A large magma chamber that solidifies underground

• A volcanic eruption

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

• Intrusive rocks form on the surface, extrusive rocks form underground

• Both form underground

• Intrusive rocks form underground, extrusive rocks form on the surface

• Both form on the surface

How does the grain size of igneous rocks relate to their cooling process?

• Larger grains indicate slow cooling

• Smaller grains indicate slow cooling

• Grain size is unrelated to cooling

• Larger grains indicate rapid cooling

What type of igneous rock is formed when lava cools extremely quickly?

• Obsidian

• Granite

• Pumice

• Basalt

Which texture is characterized by a rock being full of void spaces and cavities?

• Pyroclastic

• Vesicular

• Glassy

• Porphyritic

What causes a porphyritic texture in igneous rocks?

• Rapid cooling of lava

• Slow crystallization followed by rapid eruption

• Formation deep within the Earth

• Erosion and sedimentation

What is a key characteristic of pyroclastic texture?

• Smooth and glassy

• Full of large crystals

• Contains void spaces

• Made of angular shards

During which type of volcanic eruption is pyroclastic texture most likely to form?

• Lava flow

• Effusive eruption

• Explosive eruption

• Underwater eruption