ASVAB General Science

What is a mineral?

a naturally occurring, inorganic solid with:

• A definite chemical composition

• An orderly crystal structure

What are the building blocks of rocks?

Minerals

What are the four characteristics of a mineral?

1. Naturally occurring (made by nature, not humans)

2. Inorganic (not made from living things)

3. Solid

4. Definite chemical composition and crystal structure

If it is missing one of these characteristics, it is not a mineral.

Memory Trick:

"Nature • Not living • Solid • Structured."

How are minerals classified?

Chemical composition

Scientists group minerals based on the elements and compounds they contain.

Example of how minerals are classified.

• Quartz → made mostly of silicon and oxygen.

• Halite (table salt) → made of sodium and chlorine.

What is a rock?

A natural solid made of one or more minerals.

What can rocks also contain?

• Mineraloids (non-crystalline mineral-like substances)

• Organic remains (such as shells or plant material)

Is a Quarts a mineral or a rock?

Mineral

Is Granite a mineral or rock?

Rock

What are the three main types of rocks?

• Igneous

• Sedimentary

• Metamorphic

How is a Igneous rock formed?

Formed when magma or lava cools and hardens.

How is a Sedimentary rock formed?

Formed from layers of sediment that are compacted and cemented together.

How is a Metamorphic rock formed?

Formed when existing rocks are changed by heat and pressure.

How is a Metamorphic rock formed?

How are rocks classified?

• How they formed

• The minerals they contain

Example of how rocks are classified.

• Igneous rocks form from cooled magma or lava.

• Sedimentary rocks form from sediments.

• Metamorphic rocks form from heat and pressure.

What is a mineraloid?

A natural substance that is similar to a mineral but does not have a crystal structure.

Is a mineraloid considered a true mineral?

NO.

Mineraloids lack an orderly crystal structure.

Example: Opal

What are sedimentary rocks?

Rocks that are formed when sediments are compacted and cemented together over time.

Sedimentary rocks form in the presence of what and are found where?

They usually form in the presence of water and are often found in layers.

What is lithification?

The process that turns loose sediments into solid sedimentary rock.

How does lithification form?

• Compaction (sediments are squeezed together)

• Cementation (minerals glue the sediments together)

Why are fossils commonly found in sedimentary rocks?

Sedimentary rocks often form in water where plants and animals become buried by sediment.

Over time, these remains can become fossils.

What are the three types of sedimentary rocks?

• Detrital (Clastic)

• Biogenic

• Chemical

Describe how a Detrital (Clastic) Sedimentary rock is formed.

Made from pieces of other rocks.

Describe how a Biogenic Sedimentary rock is formed.

Made from the remains of living organisms.

Describe how a Chemical Sedimentary rock is formed.

Formed when dissolved minerals come out of water.

What does the texture of a sedimentary rock describe?

• Size of sediment grains

• Shape of sediment grains

• Arrangement of sediment particles

What does the texture of a sedimentary rock describe?

How does the texture of a Sedimentary rock help scientists?

Texture helps scientists determine how the rock formed and what environment created it.

How does the texture of a Sedimentary rock help scientists?

What does a Large, rounded grain texture of Sedimentary rock tell you?

The sediments were likely moved by water or wind over a long distance.

What does a Small, fine grains texture of Sedimentary rock tell you?

The sediments likely settled in calm water.

Why is texture important when studying sedimentary rocks?

It reveals information about the formation process of a sedimentary rock.

Scientists can use grain characteristics to determine:

• How far sediments traveled

• What transported the sediments (water, wind, ice)

• The environment where the rock formed

What does the composition of a sedimentary rock describe?

Describes the types of minerals and materials present in the rock.

What does the origin of a sedimentary rock describe?

Describes the environment where the sediments were deposited and the rock formed.

It helps identify where the sediments came from.

What are the two common origins of a sedimentary rock?

• Marine deposits

• Continental deposits

Describe Marine deposit origin of a sedimentary rock.

• Formed in ocean environments.

• Often contain remains of marine organisms.

Describe Continental deposit origin of a sedimentary rock.

• Formed on land.

• Can occur in:

  • Lakes

  • Rivers

  • Dry environments

What are igneous rocks?

rocks formed when molten rock cools and solidifies.

What type of molten material can igneous be made from?

• Magma → molten rock located below Earth's surface

• Lava → molten rock that reaches Earth's surface

How are igneous rocks formed?

Formed through the process of cooling and solidification:

Steps of how an igneous rock is formed.

1. Rock inside Earth melts due to high heat → becomes magma.

2. Magma moves through Earth's crust.

3. Magma cools and hardens into igneous rock.

If the molten rock reaches the surface, it is called lava and forms igneous rock there.

What determines the classification of an igneous rock?

Classified based on where the magma or lava cools.

The location of the cooling of magma or lava affects:

• Cooling speed

• Crystal size

• Rock type

What are the two main categories of igneous rocks?

• Intrusive igneous rocks

• Extrusive igneous rocks

Intrusive igneous rocks

• Form below Earth's surface.

• Cool slowly.

• Usually have larger crystals.

Extrusive igneous rocks

• Form on Earth's surface.

• Cool quickly.

• Usually have smaller crystals.

What are plutonic igneous rocks?

• Forms deep underground.

• Magma cools very slowly.

• Produces large crystals.

What are hypabyssal igneous rocks?

• Forms at shallow depths beneath Earth's surface.

• Cooling speed is between plutonic and volcanic rocks.

What are volcanic igneous rocks?

• Forms at Earth's surface from lava.

• Cools quickly.

• Produces small crystals or glass-like textures.

Why do intrusive igneous rocks have coarse grains?

Intrusive rocks cool slowly because they are surrounded by Earth's crust.

The slow cooling gives minerals more time to grow into large crystals, creating a coarse-grained texture.

Why do extrusive igneous rocks usually have fine grains?

Extrusive rocks cool quickly because they are exposed to the cooler environment at Earth's surface.

The rapid cooling does not allow minerals much time to form large crystals.

What is lava, and how is it related to magma?

Magma is molten rock located inside Earth.

When magma reaches Earth's surface, it is called lava.

Both magma and lava can cool and form igneous rocks.

What type of extrusive rock forms when cooling happens so quickly that crystals cannot form?

Obsidian.

When some lava cools extremely quickly, crystals do not have enough time to develop.

The result is a rock with a glassy appearance.

What are metamorphic rocks?

Rocks that have been changed from their original form by intense heat and pressure.

The rock does not melt. Instead, the existing minerals and structure are altered while remaining solid.

How are metamorphic rocks formed?

Formed when existing rocks are exposed to:

High heat
Great pressure

The forces of high heat and great pressure cause the original rock to change in:

• Structure

• Mineral composition

• Texture

The rock remains solid but becomes a new type of rock.

What happens to rocks during metamorphism?

• Deformation

• Compaction

• Bending and folding

• Changes in mineral grain size and shape

• Formation of new minerals

What is Deformation?

Changes in shape caused by pressure

How can new minerals form in metamorphic rocks?

High heat and pressure can cause chemical reactions between minerals inside the rock.

These reactions can create new minerals that were not present in the original rock.

Example:

• Limestone → Marble

Metamorphic rocks are classified into what texture groups?

1. Foliated

2. Unfoliated

What is the difference regarding how metamorphic rocks are classified by texture?

The difference depends on whether the rock develops layers or bands during metamorphism.

What are foliated metamorphic rocks?

Rocks that develop layers or bands due to pressure during metamorphism.

What are the characteristics and examples of foliated metamorphic rocks?

Characteristics:

• Layered or banded appearance

• Minerals become arranged in parallel lines

• Forms when pressure is unequal

Examples:

• Schist

• Slate (from shale)

What is Foliation?

Occurs when rock is compressed mainly from one direction (one axis), causing minerals to align into layers.

Why do foliated metamorphic rocks form layers?

Foliation forms when pressure pushes on a rock from one main direction.

The pressure causes minerals to:

• Rearrange

• Flatten

• Align into layers

This creates a visible banded texture.

What are unfoliated metamorphic rocks?

metamorphic rocks that do not have layers or bands.

When does unfoliated metamorphic rock form?

• Pressure is equal from all directions, or

• The minerals present do not create visible layering

What are the characteristics and examples of unfoliated metamorphic rocks?

Characteristics:

• No banding

• More uniform appearance

Example:

• Marble

What are fossils?

The preserved remains, impressions, or traces of ancient living organisms.

Fossils can include:

• Preserved plants

• Preserved animals

• Body remains (bones, shells, teeth)

• Traces of organisms (footprints, burrows)

What types of things can become fossils?

• Body fossils

• Trace fossils

What is a Body Fossil?

Actual parts of an organism:

• Bones

• Teeth

• Shells

• Plant material

What is a Trace Fossil?

Evidence of an organism's activity:

• Footprints

• Burrows

• Nests

What conditions are required for fossil formation?

• The organism must avoid being destroyed by:

  • Predators

  • Scavengers

• The organism must avoid decomposition (decay).

• The remains must be quickly covered by sediment.

Rapid burial preserves fossils by sediment protecting the remains from:

• Scavengers eating the remains

• Physical damage

• Exposure to oxygen that causes decomposition

The faster an organism is buried, the greater the chance it can become a fossil.

How do fossils form through mineral replacement?

During fossilization:

1. An organism is buried by sediment.

2. Over time, minerals from groundwater enter the remains.

3. The original organic material is replaced by minerals.

4. The shape and structure of the organism are preserved.

This process creates a fossil.

Memory Trick:

"Minerals replace, fossils remain."

Why are fossils commonly found in sedimentary rocks?

• Sedimentary rocks form from layers of sediment.

• Organisms can be buried quickly before they decay.

• The rocks form under conditions that preserve remains.

Igneous and metamorphic rocks usually do not contain fossils because heat and pressure can destroy remains.

Memory Trick:

"Sediments save; heat destroys."

What are the three main layers of Earth?

1. Crust

2. Mantle

3. Core

They are arranged from the outside moving inward:

🌎 Crust → Mantle → Core

What is Earth's crust?

The thin, outermost layer of Earth.

Characteristics of the Earth’s crust?

• Solid rock layer

• Where humans live

• Contains continents and ocean floors

The crust and the uppermost solid mantle together form the lithosphere.

What is Earth's mantle?

The thick layer located between the crust and the core.

Characteristics of the Earth’s mantle?

• Made mostly of solid rock

• Contains an upper and lower mantle

• Very high temperatures and pressure exist here

The mantle makes up most of Earth's volume.

What is the Upper Mantle?

• Located directly below the crust.

• The solid upper mantle combines with the crust to form the lithosphere.

What is the Lower Mantle?

• Located deeper inside Earth.

• Includes the D′ (D prime) and D″ (D double-prime) regions.

What is the lithosphere?

The rigid outer layer of Earth made of:

• Earth's crust

• The solid upper portion of the mantle

The lithosphere is broken into tectonic plates that move slowly over Earth's surface.

What is Earth's core?

Earth's innermost layer.

Earth’s core is divided into what and is made up of which metals?

It is divided into:

1. Inner Core

2. Outer Core

The core is made mostly of metals, especially:

• Iron

• Nickel

Characteristics of the Inner Core?

• Solid

• Extremely high pressure

• Located at Earth's center

Characteristics of the Outer Core?

• Liquid/molten

• Surrounds the inner core

• Creates Earth's magnetic field through moving metal

What is the order of Earth's layers from outside to inside?

From the surface moving inward:

1. Crust

2. Mantle

3. Outer Core

4. Inner Core

What is the theory of plate tectonics?

Earth's lithosphere is divided into large and small sections called tectonic plates.

These plates move slowly over the Earth's softer, more flexible upper mantle.

The theory of plate tectonics states that the movement of these plates causes major geological events such as:

• Mountains

• Volcanoes

• Earthquakes

What are tectonic plates?

Large pieces of Earth's lithosphere that move over the mantle.

Tectonic plates can be:

• Major plates (large plates)

• Minor plates (smaller plates)

The lithosphere is made of:

• Earth's crust

• Solid upper portion of the mantle

What is the lithosphere, and how is it related to plate tectonics?

Earth's rigid outer layer made of:

• Crust

• Solid upper mantle

The lithosphere is broken into tectonic plates that move across Earth's surface.

Why do tectonic plates move?

Move because of convection currents in Earth's mantle.

What is the process of how tectonic plates move?

• Heat from Earth's interior warms mantle material.

• Hot material rises.

• Cooler material sinks.

• This circular movement creates convection currents.

• These currents help move tectonic plates.

What is convection in Earth's mantle?

The transfer of heat through the movement of a fluid or material.

How does convection happen in the Earth’s mantle?

• Hot mantle material rises.

• Cooler mantle material sinks.

• This creates a cycle that contributes to tectonic plate movement.