Geology 225 Exam Three Study Guide

A collection of vocabulary flashcards covering essential terms and definitions from the lecture notes on geology.

Minerals

The building blocks of rocks.

Quartz

The most common mineral on Earth.

Flint and Chert

The first minerals ever mined on Earth.

Minerals

Any naturally occurring inorganic solid that possesses an orderly crystalline structure and a definite chemical composition that allows for some variation.

Naturally Occurring

A mineral that is naturally formed, not created in a lab.

Generally Inorganic

A mineral that does not require an organism to exist.

Solid Substance

Minerals consisting of a solid crystalline substance.

Orderly Crystalline Structure

A mineral where the atoms are arranged in an orderly, repetitive manner.

Definite Chemical Composition

Minerals that allow for some variation.

Rock

Any solid mass or mineral-like matter that occurs naturally.

Aggregate

When minerals are joined in such a way that their individual properties are retained.

Matter

Anything that has mass and occupies space.

The Four States of Matter

Plasma, Solid, Liquid, and Gas

Atoms

The smallest particles that cannot be chemically split.

Protons

Positively charges atoms

Electrons

Negatively charged atoms

Neutrons

Neutrally charged atoms

Valence Electrons

Electrons that can be transferred or shared with other atoms.

Ions

Atoms or groups of atoms with unequal numbers of protons and electrons, having a non-zero charge.

attracted

Positive and Negative Ions are _________ to one another and may stick or chemically bond together.

Bonding

Controlled by outermost shell (valence) electrons.

reactive

Elements will typically be _____ unless their valence shell is full.

Ionic Bonds

When valence electrons transfer.

Covalent Bonds

When valence electrons share.

Metallic Bonds

When electrons are free to move.

Diagnostic Properties

These are useful in identifying an unknown mineral.

Ambiguous Properties

Properties of certain minerals vary among different specimens of the same mineral.

Streak

The color of the mineral in powder form.

Opaque

When no light can transmit.

Translucent

When light shines through but no image is transmitted.

Transparent

When both light and an image are visible.

Cleavage and Fracture

How the mineral splits along weak areas.

Irregular Fracture

Produces uneven surfaces

Conchoidal Fracture

Breaks into smooth curved surfaces resembling broken glass

Tenacity

Describes a minerals resistance to breaking, bending, cutting, or other forms of deformation.

Hardness

The ability to resist scratching.

Moh’s Hardness Scale 1

Softest, can scratch with a fingernail.

Moh’s Hardness Scale 10

Hardest, cannot scratch at all.

Crystal Shape

form/shape/habit

Density

How closely its molecules are packed together.

The Formula for Density

Mass / Unit Volume

Specific Gravity

Density relative to that of water.

Striations

Straight parallel lines on the flat surfaces of crystal faces.

Magnetism

Attracted to a magnet

Double Refraction

When two images are visible when looking through the mineral.

Chemical Tests

Calcite effervesces (bubbles) in dilute HCI.

4,000

There are over _______ known minerals.

Oxygen and Silicon

The two most common elements found in minerals.

Silicates

Minerals made up of the two most common elements, oxygen and silicon.

The Silicate-Oxygen Tetrahedron

All silicates have the same fundamental building block, consisting of four oxygen ions that are covalently bonded to a comparatively smaller silicon ion.

Non-Silicate Minerals

Carbonates, Halides, Sulfates, Sulfides, Oxides, and Native Elements

Native Elements

composed entirely of one element.

Magma

Molten rock under Earth’s surface.

Lava

Molten rock above Earth’s surface.

Plate Tectonics

Earth’s surface is composed of a few large, thick plates that move slowly and change in size.

Plate Boundaries

Where tectonic plates move.

Alfred Wegner

A German meteorologist that is generally credited with developing the hypothesis of continental drift and Pangea.P

Pangea

A supercontinent proposed by Wegener.

Laurasia

Northern supercontinent containing North America and Asia.

Gondwanaland

A Southern supercontinent containing South America, Africa, India, Antartica, and Australia.

Glacial Evidence

During the late Paleozoic Era, massive glaciers covered large continental areas of the Southern Hemisphere.

Layers of Till

Sediments deposited by glaciers

Glacial Striations

Scratch marks from glaciers sliding downslope

Paleomagnetism

The remnant of magnetism in ancient rocks records the direction and intensity of Earth’s magnetic poles at the time of the rocks’ formation.

Curie Point

The temperature at which iron-bearing minerals gain their magnetization.

Polar Wandering

The apparent movements of the poles, the best explanation for such data is that the magnetic poles have remained near their present locations at the geographic north and south poles, and that the continent have moved.

Tectonic Plates

Composed of the relatively rigid lithosphere.

Divergent Boundaries

Where tectonic plates move together.

Convergent Boundaries

Where plates move together.

Ophiolites

Sequences of rock on land consisting of deep-sea sediments, oceanic crust, and upper-mantle.

Transform Boundaries

Where plates slide past one another.

San Andreas Fault

The most known transform fault.

Seafloor Spreading

The concept that the seafloor is moving like a conveyor belt away from the crest of the mid-oceanic ridge until it disappears by plunging beneath a continent or island arc.

Deep Mantle Convection

A circulation pattern driven by the rising of hot material and/or the sinking of cold material.

Marine Magnetic Anomalies

Alternating positive and negative megnetic anomalies that form a stripe-like pattern parallel to the mid-oceanic ridges, which allows us to measure the rate of movement and to predict the age of the sea floor.

The Vine-Matthews Hypothesis

New basaltic magma continually extrudes at the ridge crest and cools to record the Earth’s magnetism, including magnetic field reversals.

Transform Fault

Fracture zone segment between offset ridge crests.

Mantle Convection

May be the cause of an effect of circulation set up by ridge-push and/or slab-pull

Spreading RIdge

As the new plate moves away from the divergent boundary, it cools and thickens.

Subduction

Cold lithosphere sinking at a steep angle through the hot mantle should oull the surface part of the plate away from the ridge.

Trench Suction

If subducting plates fall into the mantle at angles steeper than their dip, then trenches and the overlying plates are pulled horizontally seaward towards the subducting plate.

Mantle Plume

Narrow columns of hot mantle rock that rise through the mantle.

The Rock Cycle

Allows us to see the many interactions among the many components and processes of the Earth’s system.

Igneous Rocks

Form as magma and lava cools and crystallize.

Extrusive Rocks (Volcanic)

Igneous rocks that solidify at Earth’s surface.

Intrusive Rocks (Plutonic)

When magma solidifies at depth.

SiO2

The most abundant constituent of igneous rocks.

Mafic

The dark silicates are rich in iron and/or magnesium and are lower in silica.

Felsic

By contrast, the light silicates are greater in potassium, sodium, and calcium are higher in silica.

Fine-Grained (Aphantic)

Crystals are too small to see with the naked eye.

Coarse-Grained (Phaneritic)

Mineral grains are large enough to identify without a microscope.

Porphyritic

Composed of two distinctly different crystal sizes.

Vesicular

Extrusive rocks containing voids left by gas bubbles that escape as lava solidifies.

Glassy

Composed of unordered atoms and resembles dark manufactures glass.

Pyroclastic (Fragmental)

A consolidation of fragments that may include ash, molten blobs, or angular blocks that were ejected due to an explosion.

Bowen’s Reaction Series

As magma cools, certain minerals will crystallize first at relatively high temperatures, while other minerals crystallize at relatively low temperatures.

Differentiation

The process by which different ingredients separate from an originally homogenous mixture.

Crystal Setting

Changes the magma composition as the crystals are removed from the melt as they settle downward.

Partial Melting

A process by which the magma composition varies as different minerals/rocks melt at different temperature.

Mechanical Weathering

When rock is broken into smaller and smaller pieces, each of which retains the characteristics of the original material.