Geology: Key Concepts and Processes

Age of the Universe

13.8 billion years

Age of the Solar System

4.6 billion years

Location of the Asteroid Belt

Between Mars and Jupiter

Difference between continental and oceanic crust

Continental crust is thicker (30-50 km) and less dense than oceanic crust (5-10 km).

Crust vs. Lithosphere

The lithosphere includes the crust and part of the upper mantle.

Wegener's evidence for continental drift

Lacked a mechanism for movement.

Layer forming tectonic plates

Lithosphere

Driving force of tectonic plate motion

Mantle convection and gravity

Process at a subduction zone

One plate sinking beneath another

Difference between island arcs and continental volcanic arcs

Island arcs form from oceanic-oceanic collisions, while continental arcs form from oceanic-continental collisions.

Mantle plume (hotspot)

A region where magma rises from deep within the mantle to the surface.

Criteria for classifying a mineral

Must be solid, inorganic, naturally occurring, have a crystalline structure, and a definite chemical composition.

Relative vs. absolute ages of rocks

Absolute age uses radioactive decay to determine the exact time, while relative age is comparative.

Ways magma is produced within the Earth

Decompression, addition of volatiles, heat transfer

Type of melting not occurring in the mantle

Solidification

Main textures of igneous rocks

Fine-grained, coarse-grained, glassy, and vesicular textures

Change in magma composition as it rises

Crystallization, assimilation of surrounding rocks, and mixing with other magmas

Difference between magma and lava

Magma is molten rock underground; lava is molten rock that has erupted to the surface.

Viscosity and its relationship with silica content, temperature, and gas content

Higher silica increases viscosity; higher temperature and gas decrease viscosity.

Viscosity

A measure of a fluid's resistance to flow.

Silica

A chemical compound that increases the viscosity of magma.

Temperature

A factor that affects the viscosity of magma; higher temperatures decrease viscosity.

Rhyolite

A type of magma that is more viscous due to its high silica content.

Basalt

A type of magma that has low silica content and is less viscous than rhyolite.

Shield Volcanoes

Volcanoes formed at hotspots where magma rises to the surface.

Composite Volcanoes

Volcanoes formed from subduction processes.

Intermediate to Felsic Volcanic Eruptions

Eruptions that produce hazards such as ash falls, pyroclastic flows, and lava flows.

Pyroclastic Flow

A fast-moving current of hot gas and volcanic matter that is denser than a surge.

Surge

A less dense and faster-moving phenomenon compared to a pyroclastic flow.

Physical Weathering Processes

Processes that break down rocks into smaller pieces without changing their composition.

Lithification

The process by which sediments compact and are cemented by minerals to form rock.

Evaporite Minerals

Minerals that crystallize from evaporating water in arid environments.

Chemical Sedimentary Rocks

Rocks that can form both organically and inorganically, such as limestone and chert.

Silica (SiO2)

A compound that dominates deep-sea sediments due to the dissolution of carbonate.

Fossils

Remains or traces of ancient organisms preserved in rock.

Lagerstätten

Fossil deposits with exceptionally preserved organisms, providing insights into ancient ecosystems.

Drainage Basin

The area from which all precipitation flows to a single stream, divided by drainage divides.

Braided Streams

Streams that have multiple channels, high sediment load, and variable flow velocity.

Water Table

The level below which the ground is completely saturated, separating saturated and unsaturated zones.

Water table

The level below which the ground is completely saturated; it separates saturated and unsaturated zones.

Aquifers

Porous and permeable rock layers that store groundwater.

Porosity

The measure of how much empty space is in a material, affecting how much water it can hold.

Permeability

The ability of a material to allow fluids to pass through it.

Saltwater intrusion

The process where freshwater is replaced by saltwater, leading to contamination, especially when groundwater is overpumped near the coast.

Calderas

Large depressions formed when a large eruption drains a magma chamber, causing the surface to collapse.

Sinkholes

Depressions that form when underground water dissolves limestone, causing the ground to collapse.

Lithosphere

A solid, rigid layer of the Earth.

Asthenosphere

The uppermost part of the mantle that is partially molten and flows.

Continental rift

A geological feature where the continental crust separates, allowing magma to rise and create new oceanic crust.

Seafloor spreading

The process where oceanic plates move apart, and magma fills the gap, forming new crust.

Convergent boundary

A type of plate boundary that can lead to mountain building due to continuous subduction.

Mid-ocean ridges

Locations where new crust is created as oceanic plates diverge.

Subduction zones

Areas where crust is destroyed as it is recycled back into the mantle.

Minerals

Naturally occurring, inorganic solids with a definite chemical structure and crystalline form.

Relative dating principles

Cross-cutting, inclusions, superposition, original horizontality, lateral continuity, faunal succession.

Disconformities

Gaps in parallel layers of sedimentary rock indicating interruptions in deposition.

Angular disconformities

Tilting of rock layers that indicates a period of erosion or non-deposition.

Nonconformities

Contacts between sedimentary rocks and older igneous or metamorphic rocks.

Vesicular texture

A texture that forms when gas bubbles are trapped in magma as it cools.

Groundwater

Water that is stored underground in aquifers.

Grain size

The size of individual particles in a sediment or rock, affecting porosity and permeability.

Sorting

The distribution of grain sizes in a sediment, influencing porosity and permeability.

Shape

The form of grains in sediment, which can affect how easily water flows through them.

Eruptions

Explosive events that can lead to the formation of calderas.

Groundwater contamination

The presence of pollutants in groundwater, often due to saltwater intrusion.

Pyroclastic flow

A fast-moving current of hot gas and volcanic matter.

Lahar

A volcanic mudflow; they can travel rapidly and bury communities.

Pahoehoe

Smooth, ropy lava flow.

'A'a

Rough, jagged lava flow.

Ashfall

Falling ash from an eruption, which settles from the air.

Pyroclastic surge

A fast-moving, dense current of gas and volcanic debris.

Felsic flow

A type of lava flow that is high in silica and usually more viscous.

Basaltic surge

A fast-moving flow of basaltic lava, typically less viscous.

Basaltic eruptions

Eruptions that produce high-temperature lava flows, toxic gases, and minor ashfall.

Volcanic gases

Gases released during eruptions that can be toxic and affect environments.

Caldera

A large depression formed when a volcano collapses after a major eruption.

Chemical weathering processes

Processes that alter the chemical composition of minerals, including dissolution, oxidation, hydrolysis, and carbonation.

Sediment transport

The movement of sediment from source to sink, where it is sorted by size and rounded.

Carlsbad Caverns

Caves formed by sulfuric acid dissolution, making them unique compared to other limestone caves.

White Sands

Formed from wind-blown gypsum deposits left behind after an ancient lake dried up.

K-T event

An event that occurred 65 million years ago, caused by a meteorite impact, marking the extinction of the dinosaurs.

Permian Extinction

The largest known mass extinction event, occurring around 252 million years ago, wiping out 90-95% of species.

Meandering stream

A stream where erosion occurs on the outside bend and deposition occurs on the inside bend.

Flash flooding

A common type of flood in southern New Mexico, caused by intense, short rain events over dry terrain.

Flood hazards

6 inches of water can stall a passenger car, while 2 feet can carry it away.

Groundwater recharge

The process affected by roads and man-made structures, which decreases recharge by increasing runoff and reducing infiltration.

Overpumping groundwater

Land subsidence and reduced water availability.

Metamorphism

Metamorphism occurs when rocks are subjected to conditions that alter their structure and mineral composition, but without becoming molten.

Foliation

Foliation occurs when minerals align under directional pressure, forming parallel layers or bands.

Contact metamorphism

Contact metamorphism happens near magma intrusions, while regional metamorphism is due to pressure and heat over large areas.

Glacier formation

Glaciers form from the accumulation and compaction of snow in regions where snowfall exceeds melting.

Continental glaciers

Continental glaciers cover large regions like Antarctica, while alpine glaciers form in mountainous areas.

Glacial erosion features

Glaciers carve out U-shaped valleys, fjords, and depressions known as cirques during their movement.

Wind erosion in deserts

Wind erodes and deposits sand, forming dunes and deflation basins.

Desert pavement

A surface of tightly packed stones left after wind removes finer particles.

Coastal landscape shaping

Coastal landscapes are primarily shaped by the action of waves, tides, and ocean currents.

Longshore current

A current parallel to the shore that transports sand and reshapes coastlines.

Renewable resources

Renewable resources can be regenerated quickly, like solar energy, while non-renewable resources, like fossil fuels, take millions of years to form.

Human impact on landscapes

Human activities like mining, deforestation, and urbanization alter landscapes and deplete resources.