Rocks and Minerals Practice Exam Flashcards

A set of flashcards based on the lecture notes covering rock types, the rock cycle, minerals, weathering/erosion, and geological dating principles.

What is the definition of a rock according to the lecture notes?

A rock is a naturally occurring collection of one or more minerals.

What is the rock cycle?

It is a continuous geological process where rocks are broken down, transported, and reformed from one type of rock into another type of rock over a period of time.

How are Igneous Rocks formed?

Igneous rocks are formed through slow (inside the Earth) or fast (outside the Earth) cooling of magma.

In terms of cooling time and texture, how is an Extrusive Igneous Rock characterized?

Cooling time: seconds to months; Texture: invisible or microscopic grains.

What is the cooling time and texture for Intrusive Igneous Rocks?

Cooling time: thousands of years; Texture: small-to-medium grains.

How are Plutonic Igneous Rocks defined based on cooling time and texture?

Cooling time: millions of years; Texture: large grains.

How does the rate of cooling affect the texture of an igneous rock?

Slow cooling allows large crystals to form (coarse grained), and fast cooling yields small crystals (fine grained).

What are Sedimentary Rocks?

Compressed layers of sediment over time that have distinct layering and bedding, formed from pre-existing rocks or pieces of organisms.

What are Clastic Sedimentary Rocks?

Rocks formed from the accumulation of sediments that are compacted into a rock.

How are Chemical Sedimentary Rocks formed?

They form when dissolved minerals precipitate out of solution.

What are Organic Sedimentary Rocks?

Rocks formed from the accumulation of organic material, such as Coal.

How are Metamorphic Rocks created?

They are created when previous igneous, sedimentary, or metamorphic rocks are subjected to heat and pressure.

What factor determines the specific type of metamorphic rock that will be made?

The intensity of the heat and pressure.

What is the definition of a crystal?

A solid material whose atoms, molecules, or ions are arranged in an orderly, repeating pattern.

What five characteristics do all minerals contain?

Solid, inorganic, naturally occurring, a definite chemical composition, and a regular three-dimensional arrangement of atoms.

What is an element?

A substance that cannot be broken down into simpler substances by chemical means and is composed of atoms with identical atomic numbers.

What is a native-element mineral?

Minerals that consist of only one element.

Are most minerals native-element minerals?

No; most minerals are a combination of multiple elements, as there are over $3000$ minerals but only $118$ elements.

What is a key difference between a rock and a mineral?

Rocks are made of multiple types of minerals, and the same rock can contain different amounts of each mineral while remaining the same type of rock.

What term is used for rocks that contain valuable minerals?

An Ore.

How are atoms arranged in a mineral?

Atoms are arranged in a regular and repeating three-dimensional arrangement that never changes.

What is the process of physical weathering?

The process where rock is broken down by physical forces or processes including gravity, water, ice, wind, or human actions at or near Earth’s surface.

Define erosion.

The wearing away of soil or rock by weathering, mass wasting, and the action of streams, glaciers, waves, wind, and underground water.

What is mass wasting?

The downhill movement of material under the influence of gravity.

Why is igneous rock less susceptible to erosion?

It is more dense than other rock types.

What is the primary difference between weathering and erosion?

Weathering breaks down rocks in place on Earth's surface, while erosion transports these materials away.

What happens to the density of rocks when they melt?

The density of the rocks decreases in their liquid form.

What happens to magma below the Earth's crust due to its change in density?

The lower density magma tries to rise to the surface.

How can you visually distinguish intrusive from extrusive igneous rocks?

By the grain size/size of crystals; Intrusive rocks have large grains, and extrusive rocks have very small grains.

What is the definition of sediment in Earth science?

Small or broken up pieces of rock that have been moved from one place to another.

What is the most common type of rock found on Earth's surface?

Sedimentary rocks.

Describe the process of sedimentary rock formation.

Sediments are buried deep underground and squished together; water containing minerals then fills the space and hardens, cementing the pieces together.

What is the process called when dissolved minerals are left behind as a solid?

Precipitation or a precipitant.

Why are sedimentary rocks useful for understanding past environments?

They are changed very little over time.

What condition must be met for heat and pressure to form metamorphic rocks from other rocks?

The environment must be deep underground and hot, but not hot enough to melt the rocks.

What is regional metamorphism?

When extremely large sections of rock (hundreds of square miles) are forced underground near faults.

What causes contact (localized) metamorphism?

Magma rising up from deep within the earth and heating the rocks nearby.

Why is gold in California often found near faults?

Faults like the San Andreas Fault concentrate large quantities of minerals, including gold, into layers over time.

What is deformation?

The process where rocks bend, break, or change texture due to forces that push, pull, or heat them.

What does the term foliation mean in metamorphic rocks?

It describes layers of minerals lining up perpendicular to the direction of force, making minerals look like a flat pancake from being squished.

What is a geological time scale?

The division of geologic times based on evolutionary events of geologic history.

In geologic time, compare an epoch, period, and era.

An epoch is a short division; a period contains two or more epochs; and an era is a major division containing two or more periods.

How do scientists determine the absolute age of rocks?

They measure the radioactive decay of radioactive minerals within the rocks.

What is radioactive decay?

The process by which an atomic nucleus of an unstable atom loses atomic particles, forming a new lighter element and becoming less radioactive.

What is a half-life?

The length of time it takes for half of a radioactive substance to decay.

What is Earth's oldest mineral and what is its age?

Zircon, which has samples dating as far back as $4$ billion years.

Why is radiocarbon dating only effective for young samples?

The half-life of radioactive carbon is short ($5730$ years), and after $70000$ years, the amount of remaining non-decayed carbon is tiny.

What is relative dating?

Determining the age of an object or event in comparison to other objects or events without providing a specific numerical age.

What is the law of superposition?

The geological principle stating that the youngest layer of rock is on the top and the oldest layer is on the bottom.