Geology and Earth History Lecture Flashcards

This flashcard set covers fundamental geology concepts including plate tectonics, Earth's internal structure, mineralogy, volcanology, rock types, weathering, seismology, and geologic history based on the lecture transcript.

Mantle Convection

The process where hot mantle material rises while cooler mantle sinks, creating convection currents that move tectonic plates.

Ridge Push

A process where gravity causes plates to slide away from the elevated mid-ocean ridge.

Slab Pull

The process where dense oceanic lithosphere sinks into the mantle at subduction zones and pulls the rest of the plate behind it.

Slow-spreading Ridges

Ridges with a spreading rate of about $1–5\,cm$ per year, such as the Mid-Atlantic Ridge.

Fast-spreading Ridges

Ridges with a spreading rate of about $10–15\,cm$ per year, such as the East Pacific Rise.

Divergent Boundaries

Plate boundaries where plates move apart and new oceanic crust forms, characterized by mid-ocean ridges, rift valleys, shallow earthquakes, and basaltic volcanism.

Convergent Boundaries

Plate boundaries where plates move together causing subduction or continental collision, characterized by trenches, volcanic arcs, mountain building, and deep or shallow earthquakes.

Transform Boundaries

Plate boundaries where plates slide horizontally past each other, characterized by strike-slip faults and frequent earthquakes with little volcanism.

Continental Crust

The silicate layer of Earth mainly composed of granite-rich rocks.

Oceanic Crust

The silicate layer of Earth mainly composed of basalt-rich rocks.

Mantle

The chemical layer of Earth composed of ultramafic rocks rich in magnesium and iron.

Core

The chemical layer of Earth mainly composed of iron and nickel, consisting of a liquid outer layer and a solid inner sphere.

Lithosphere

The rigid outer shell of Earth made of the crust and uppermost mantle.

Asthenosphere

A weak, plastic layer of the upper mantle located beneath the lithosphere.

Mesosphere

The stronger lower mantle located beneath the asthenosphere.

Nebular Hypothesis

The preferred hypothesis for solar system formation where a giant cloud of gas and dust collapses due to gravity into a rotating disk.

Planetesimals

Small solid bodies formed when dust particles collide and stick together during the formation of the solar system.

Protoplanets

Larger bodies formed when planetesimals combine.

Olivine

A mineral structure containing isolated tetrahedra, commonly found in the mantle and mafic igneous rocks.

Pyroxene

A mineral structure containing single chains of tetrahedra.

Amphibole

A mineral structure containing double chains of tetrahedra.

Sheet Silicates

Minerals consisting of mica and clay.

Framework Silicates

Minerals consisting of quartz and feldspar, commonly formed in igneous rocks.

Ionic Bonding

Bonding caused by the transfer of electrons between atoms, commonly occurring between metals and nonmetals as seen in Halite ($NaCl$).

Covalent Bonding

Bonding caused by the sharing of electrons between nonmetals, such as in Diamond.

Metallic Bonding

Bonding where electrons move freely among metal atoms.

Van der Waals Bonding

Weak attractions between molecules or layers, such as in Graphite.

Mineral

A substance that is naturally occurring, inorganic, solid, has a crystalline structure, and a definite chemical composition.

Calcite

A carbonate mineral commonly formed in marine environments.

Shield Volcanoes

Broad volcanoes with gentle slopes formed from basaltic lava, common at hotspots like Hawaii.

Composite Volcanoes

Steep-sided volcanoes with explosive eruptions, common at convergent plate boundaries.

Cinder Cones

Small, steep volcanoes made mostly of pyroclastic material.

Lava Domes

Volcanoes formed by very viscous lava with explosive potential.

Intrusive Igneous Rock

Rock that cools slowly underground, resulting in a coarse-grained texture with large crystals; Granite is a primary example.

Extrusive Igneous Rock

Rock that cools quickly at Earth’s surface, resulting in a fine-grained or glassy texture with small crystals; Basalt is a primary example.

Mechanical Weathering

The physical breakdown of rock without changing composition, examples include frost wedging, root growth, and abrasion.

Chemical Weathering

The breakdown of rock through chemical reactions such as hydrolysis, oxidation, and dissolution.

Sediment Sorting

The degree to which sediment grains are similar in size; well-sorted indicates consistent energy like beaches, while poorly sorted indicates rapid deposition like glaciers.

Lithification

The two-step process of compaction and cementation that converts sediment into sedimentary rock.

Metamorphism

The alteration of rock by heat, pressure, and chemically active fluids, leading to recrystallization and foliation.

P-waves

Fast compressional seismic waves that travel through both solids and liquids.

S-waves

Slower shear waves that only travel through solids.

Normal Fault

A fault caused by tension where the hanging wall moves downward, typically found at divergent boundaries.

Reverse Fault

A fault caused by compression where the hanging wall moves upward, typically found at convergent boundaries.

Strike-slip Fault

A fault with horizontal movement caused by shear stress, commonly found at transform boundaries.

Earthquake Magnitude

A measure of the energy released during an earthquake, measured by the Richter Scale and Moment Magnitude Scale.

Earthquake Intensity

A measure of the observed damage caused by an earthquake, measured by the Modified Mercalli Scale.

Brittle Deformation

Deformation in the shallow crust where rocks break under stress, forming faults and fractures.

Ductile Deformation

Deformation in the deeper crust where rocks bend or flow under stress, forming folds and foliation.

Anticline

An upward arch-shaped fold with the oldest rocks in the center.

Syncline

A downward trough-shaped fold with the youngest rocks in the center.

Principle of Superposition

The relative dating principle that older rock layers are found beneath younger layers.

Relative Dating

Determining the sequence of geologic events using principles like superposition and cross-cutting relationships without exact ages.

Absolute Dating

Determining numerical ages of rocks using radioactive decay.

Half-life

The time required for half of a radioactive parent isotope to decay into a stable isotope.

Great Oxidation Event

A rise in atmospheric oxygen about $2.4$ billion years ago caused by oxygen released by photosynthetic cyanobacteria.

Banded Iron Formations

Iron-rich layers formed when oxygen reacted with dissolved iron in the oceans during the Great Oxidation Event.

Permian Extinction

The largest mass extinction in Earth history.

Dinosaur Extinction

An event caused by an asteroid impact about $66$ million years ago.