Geology Vocabulary Flashcards

Vocabulary flashcards covering key geoscience concepts from the lecture notes.

Exponential growth

A growth pattern where the growth rate is proportional to the current population size; the larger the population, the faster it grows.

Industrial Revolution

Period that enabled population growth by improving public health, medicine, sanitation, and related conditions.

Life expectancy

Average number of years a person can expect to live; has risen over history (about 30 years a thousand years ago).

Population density

Number of people per unit area; varies by region and influences risk exposure to hazards.

Mid-latitudes

Latitudes roughly between 30° and 60°; climates are temperate and heavily populated regions often lie here.

Temperate zone

Climate zone with moderate temperatures, commonly along western margins of continents and favorable for settlement.

Plate boundary

Line where two tectonic plates meet; movement here drives earthquakes and volcanoes.

Subduction zone

A type of plate boundary where one plate sinks beneath another into the mantle.

Pacific Ring of Fire

A major basin-wide belt in the Pacific Ocean highly susceptible to earthquakes and volcanic eruptions. This activity is predominantly driven by the extensive network of subduction zones, where oceanic plates converge and plunge beneath other plates, generating magma that fuels volcanism and stresses that cause frequent seismic events. It's a 40,000 km (25,000 miles) horseshoe-shaped region accountable for roughly 90\% of the world's earthquakes and 75\% of its active volcanoes.

Continental crust

The less dense, thicker portion of Earth's crust that forms the continents and continental shelves. It is primarily composed of granitic rocks, rich in silica and aluminum, making it significantly lighter than oceanic crust (approximately 2.7 \text{ g/cm}^3). This crust is considerably older on average, with some parts dating back billions of years, and is characterized by its buoyancy, which prevents it from being easily subducted.

Oceanic crust

The denser, thinner portion of Earth's crust that primarily underlies the ocean basins. It is predominantly composed of basaltic rocks, which are rich in iron and magnesium, giving it a density of approximately 3.0 \text{ g/cm}^3. In contrast to continental crust, blank is relatively young, as it is continuously generated at mid-ocean ridges through seafloor spreading and recycled back into the mantle at subduction zones.

Lithosphere

The rigid outermost mechanical layer of Earth, comprising the crust and the brittle uppermost part of the mantle. It is fractured into a number of large and small tectonic plates that move independently over the more ductile asthenosphere. The thickness of the lithosphere varies significantly, ranging from approximately 5-100 km beneath ocean basins (oceanic lithosphere) to about 150-200 km or more beneath continents (continental lithosphere). Its rigidity is crucial for plate tectonics, as it allows for the transmission of stress and the occurrence of earthquakes.

Asthenosphere

The mechanically weak and ductile layer of Earth's upper mantle that lies directly beneath the lithosphere. Characterized by high temperatures and pressures, its rocks are solid but behave plastically, allowing them to flow slowly over geological timescales. This convection within the blank is the primary driving force behind the movement of tectonic plates in the overlying lithosphere. Its depth typically ranges from approximately 100 km to 700 km below the surface, acting as a crucial zone for magma generation and plate tectonics.

Mesosphere

refers to the lower part of the Earth's mantle, situated between the ductile asthenosphere above and the liquid outer core below. Extending from a depth of approximately 660 km down to about 2,900 km, this region is characterized by increasing pressure and temperature, but due to these extreme conditions, the rocks, primarily silicates like bridgmanite and ferropericlase, remain solid and very rigid. Despite its solid state, the high temperatures allow for very slow convection currents over geological timescales, playing a role in the overall dynamics of plate tectonics, though it is much less ductile than the asthenosphere.

Outer core

Liquid iron-nickel layer surrounding the inner core; generates Earth's magnetic field.

Inner core

Solid iron-nickel center of the Earth.

Mantle

Solid rock layer between the crust and core; makes up most of Earth's volume; contains rocks like peridotite.

Granite

Light-colored, coarse-grained rock; typical composition of continental crust; less dense than basalt.

Basalt

Dense, dark, fine-grained rock; main component of oceanic crust.

Sedimentary rocks

Rocks formed from the accumulation, burial, and compaction of weathered sediments, minerals, or organic matter. They are characterized by their layered structure and are the only rock type in which fossils are preserved.

Sandstone

Sedimentary rock formed from sand-sized grains; gritty texture.

Shale (Mudstone)

Fine-grained sedimentary rock formed from clay/mud.

Limestone

Sedimentary rock formed from calcium carbonate in lime mud; often fossil-rich.

Erosion

Process by which weathered material is transported away by water, wind, or ice.

Weathering

Breakdown of rocks at or near the surface by mechanical or chemical processes.

Delta

Flat area at a river mouth where sediment is deposited; Bangladesh is a notable example.

River floodplain

Flat land beside a river prone to flooding; typically fertile and densely populated.

Density differentiation

The process during Earth's early, molten phase where materials separated by density: denser substances (like iron-nickel) sank to form the core, and lighter silicates rose to form the mantle and crust. This gravitational sorting established Earth's layered internal structure, vital for its geological dynamics.

Density (geology values)

1 g/cm3 for water; continental crust ~2.7 g/cm3; oceanic crust ~3.0 g/cm3; mantle ~3.3 g/cm3; core is densest.

Rock cycle

Concept describing the transformations among igneous, sedimentary, and metamorphic rocks over time.

Cross sectional view

A cut-through view showing the interior structure of an object, like Earth’s interior layers.

Map view

A view from above showing the surface features and topography of a area.

Igneous Rocks

Rocks formed through the cooling and solidification of molten magma or lava. They are classified based on their formation location:

• Plutonic (Intrusive) Rocks: Formed when magma cools slowly beneath Earth's surface, resulting in large crystals (e.g., granite). (continental crust)

• Volcanic (Extrusive) Rocks: Formed when lava cools quickly on or near Earth's surface, resulting in fine-grained or glassy textures (e.g., basalt). (oceanic crust)

Metamorphic Rocks

Rocks formed from existing rocks (igneous, sedimentary, or other blank rocks, known as \"protoliths\") that undergo significant changes due to intense heat, pressure, or chemically active fluids. These conditions, typically found deep within Earth's crust, cause the rocks to recrystallize, resulting in new mineral compositions