Geology: Plate Boundaries, Mineral Properties, and Igneous Rocks

What is a convergent boundary?

A boundary where two tectonic plates move toward each other, sometimes resulting in subduction zones.

What is a divergent boundary?

A boundary where two tectonic plates move away from each other, sometimes creating continental or oceanic rifts.

What type of stress is associated with convergent boundaries?

Compressional stress.

What type of stress is associated with divergent boundaries?

Tensional stress.

What is cleavage?

Visible planes of weakness in a mineral that are representative of its atomic structure.

What can cleavage planes tell you about a mineral?

They can help identify the mineral; a mineral can have several cleavage planes.

What is hardness?

A mineral's resistance to being scratched by a hard external material.

What scale is used to measure mineral hardness?

Mohs hardness scale.

What tools are used to assess mineral hardness?

A fingernail, penny, knife, nail, and drill, in increasing order of hardness.

How is mineral hardness reported?

Using the value or range determined from the Mohs hardness scale.

What is luster?

The way a mineral's appearance interacts with light.

What are the two major categories of luster?

Metallic and non-metallic.

How can you recognize metallic luster?

The mineral has a metallic-looking appearance; metallic minerals are usually heavier.

What is streak?

The color produced when a mineral is scraped against a surface.

How do you test a mineral's streak?

Scrape the mineral against a streak plate and observe the color it produces.

What should you know about the minerals from the mineral lab?

Be familiar with the minerals you examined and their identifying properties.

What is an intrusive igneous rock?

An igneous rock formed beneath Earth's surface that cools slowly.

What is an extrusive igneous rock?

An igneous rock formed at Earth's surface that cools quickly.

How can you visually distinguish intrusive and extrusive igneous rocks?

By crystal size: intrusive rocks have larger crystals because they cool slowly, while extrusive rocks have smaller crystals because they cool quickly.

What are common minerals in igneous rocks?

Potassium feldspar, quartz, plagioclase feldspar, pyroxene, and olivine.

What is a clast?

A fragment of a sedimentary rock.

What is a phaneritic texture?

A texture with visible, compact crystals; associated with intrusive igneous rocks.

What is an aphanitic texture?

A texture in which crystals are too small/plain to see easily.

What is a porphyritic texture?

A texture with scattered larger crystals within a finer-grained material.

What igneous textures are associated with extrusive rocks?

Glassy, vesicular, and pyroclastic.

What igneous textures are associated with intrusive rocks?

Phaneritic, aphanitic, and porphyritic.

What is foliation?

Layering of minerals within a metamorphic rock.

Which main metamorphic rocks exhibit foliation?

Shale, slate, phyllite, schist, and gneiss.

What produces foliation?

Extreme heat and pressure during metamorphism.

How can you visually determine the degree of metamorphism?

By examining mineral layering.

Which rocks represent low metamorphic grade?

Shale and slate.

Which rock represents middle metamorphic grade?

Phyllite.

Which rocks represent high metamorphic grade?

Schist and gneiss.

What is a protolith?

The original rock before it undergoes metamorphism.

Give an example of a protolith.

Limestone is the protolith of marble.

What does composition mean when describing an igneous rock?

The amount of silica in an igneous rock.

What are the four categories of igneous rock composition?

Felsic, intermediate, mafic, and ultramafic.

Which igneous composition has high silica content?

Felsic.

Which igneous composition has very low silica content?

Ultramafic.

What mineral is commonly associated with ultramafic rocks?

Olivine, which often gives them a green color.

List some intrusive igneous rocks

Granite, diorite, gabbro, and peridotite.

List some extrusive igneous rocks

Rhyolite, andesite, basalt, and komatite.