Chapter 20 HW

What is the difference between a dike and a sill?

A dike intrudes across sedimentary layers, and a sill intrudes between sedimentary layers.

What do freeze-thaw and salt weathering have in common?

Both freeze-thaw and salt weathering require rain and force rocks apart physically.

In general, why does Earth's crust sit on top of the mantle?

Earth's crust is less dense than the mantle.

How are felsic magmas formed?

Heat from the mantle melts part of the lower crust.

In Earth's interior, does temperature increase or decrease with depth?

Increases.

What is the most abundant element for Earth as a whole?

Iron

Could metamorphic rocks reach the surface of a planet without rock-uplifting processes?

No, metamorphic rocks must be uplifted and exposed by erosion.

How are metamorphic rocks formed?

Preexisting rock is altered through heat and pressure.

How do mafic volcanic rocks get to Earth's surface?

Pressure from overlying crust forces mantle magmas through cracks to Earth's surface. These magmas erupt out of volcanoes, cool, and solidify into rock.

Why are volcanic rocks often exposed at Earth's surface as hills, ridges, and mountains surrounded by areas of lower elevation?

Volcanic rocks are often more resistant to erosion than surrounding rock.

Why does water frozen in the cracks of a rock help to break down the rock?

Water expands when frozen and physically forces the rock apart.

In general, when will melted rock in the mantle rise?

almost always

What is a magma chamber called after the conduit has solidified and been exposed by erosion?

batholith

Where do most metamorphic rocks form?

between a few and many kilometers beneath Earth's surface

What is the most abundant mineral in Earth's crust?

feldspar

What lies underneath volcanic features at Earth's surface?

magma chambers and volcanic conduits

What is the most abundant element in Earth's crust?

oxygen

What is the second most abundant mineral?

quartz

What is the second most abundant element?

silicon

What is salt weathering?

the formation of minerals in rock cracks during the evaporation of salty water, forcing rock apart

As minerals crystallize in cooling magma, which minerals are the first to crystallize: the minerals with lower amounts of silica or the minerals with higher amounts of silica?

the minerals with lower amounts of silica

How do metamorphic rocks reach Earth's surface?

through removal of overlying rocks

What is a volcanic conduit called after the conduit has solidified and been exposed by erosion?

volcanic neck

When will magma rise to Earth's surface?

when the magma is less dense than adjacent rock