Geologic Processes and the History of the Earth

Comprehensive vocabulary flashcards covering exogenic and endogenic geologic processes, relative and absolute dating principles, and the geologic time scale.

Geologic Processes

Natural processes that continuously change the physical structure and appearance of Earth by forming rocks, building mountains, creating or destroying landforms, and causing events like earthquakes.

Exogenic Processes

Geologic processes occurring at or near Earth's surface that are driven primarily by external forces such as solar energy, water, wind, ice, gravity, and organisms.

Endogenic Processes

Geologic processes originating within Earth that are driven by internal heat and energy, including earthquakes, volcanism, faulting, folding, and mountain building.

Weathering

The in-place breakdown or alteration of rocks and minerals at or near Earth's surface without involving the transportation of materials.

Physical Weathering

The mechanical breakdown of rocks into smaller fragments without altering their chemical or mineral composition.

Frost Wedging

A mechanical weathering process in which water seeps into rock cracks, freezes, expands, and exerts outward pressure that splits the rock over repeated freeze-thaw cycles.

Abrasion

The mechanical wearing down and scraping of rocks and sediments as they collide with one another via moving water, wind, or glacial ice.

Exfoliation

A physical weathering process where curved outer rock sheets or slabs peel away from underlying rock due to pressure release and expansion.

Chemical Weathering

The decomposition and alteration of minerals in rocks through chemical reactions with substances such as water, oxygen, carbon dioxide, and environmental acids.

Oxidation (Weathering)

A chemical weathering reaction in which environmental oxygen combines with iron-bearing minerals to produce reddish or brownish alteration products similar to rust.

Carbonation

A chemical weathering process where dissolved carbon dioxide forms weak carbonic acid in water, which reacts with and dissolves minerals, particularly those found in limestone.

Hydrolysis

A chemical weathering reaction in which minerals react directly with water to form entirely new minerals.

Biological Weathering

The disintegration and alteration of rocks caused directly or indirectly by the activities of living organisms, such as plant roots, lichens, burrowing animals, and humans.

Erosion

The geological process involving the detachment, removal, and transport of weathered rock materials and soil from their source location.

Deposition

The settling, dropping, or accumulation of transported sedimentary particles in a new resting place when transport agents lose kinetic energy.

Mass Wasting

The downslope movement of soil, rock fragments, and regolith driven directly by gravity without requiring a transporting medium like water or wind.

Divergent Boundary

A tectonic plate boundary where two lithospheric plates pull apart, leading to rifting, mid-ocean ridges, and the formation of new crust.

Convergent Boundary

A tectonic plate boundary where plates collide or move toward each other, forming mountain ranges, subduction zones, volcanic arcs, and deep trenches.

Transform Boundary

A plate boundary where tectonic plates slide horizontally past each other, characterized by major fracture systems and frequent earthquakes.

Fault

A planar fracture or discontinuity in Earth's crust along which observable relative displacement and movement of rock blocks has taken place.

Folding

The permanent ductile bending of flat rock strata resulting from compressional tectonic forces, typically forming anticlines and synclines.

Orogeny

The tectonic process of mountain building, commonly driven by convergent plate margins where crustal rocks are compressed, folded, faulted, and uplifted.

Stratified Rocks

Rocks that exhibit distinct sedimentary layering called strata, produced by continuous cycles of weathering, erosion, deposition, compaction, and cementation.

Relative Dating

The technique of placing geological events, rock layers, or fossils in a chronological sequence to establish which is older or younger without specifying an age in years.

Law of Superposition

The stratigraphic principle stating that in an undisturbed sedimentary rock succession, the oldest layer is situated at the bottom and layers become progressively younger toward the top.

Principle of Original Horizontality

The geological principle stating that layers of sediment are initially deposited in nearly flat, horizontal sheets under the influence of gravity.

Principle of Cross-Cutting Relationships

The relative dating rule establishing that an igneous intrusion, fault, or fracture that cuts across pre-existing rock bodies must be younger than the units it disrupts.

Principle of Inclusions

The stratigraphic concept stating that pieces or fragments of rock preserved inside an enclosing rock mass must be older than the host rock containing them.

Principle of Faunal Succession

The principle that distinct fossil assemblages succeed each other vertically in a specific, reliable, and predictable order through geologic time.

Absolute Dating

A quantitative dating method used to establish the precise numerical age of a rock, mineral, fossil, or geologic event expressed in calendar years.

Radiometric Dating

An absolute dating technique based on measuring the known, steady rate of radioactive decay converting unstable parent isotopes into stable daughter products.

Half-Life

The exact interval of time required for half ($50\%$) of the radioactive parent atoms in a closed system to decay into stable daughter atoms.

Geologic Time Scale

A hierarchical chronological framework categorizing Earth's approximately $4.6\text{ billion-year}$ history into eons, eras, periods, and epochs according to significant biotic and physical events.

Marker Fossils

Readily identifiable, abundant fossils of organisms that possessed wide geographic distribution and a short geologic lifespan, utilized to correlate and date rock layers.

Stratigraphic Correlation

The process of demonstrating that rock layers or strata separated geographically are equivalent in geologic age and stratigraphic position based on rock properties and marker fossils.

Phanerozoic Eon

The most recent eon in Earth's history, marked by an abundant fossil record and rapid diversification of multicellular organisms with hard parts.

Paleozoic Era

The era of 'Ancient Life' within the Phanerozoic Eon, characterized by the expansion of marine organisms, the colonization of land, early reptiles, trilobites, and ending with the Permian extinction.

Mesozoic Era

The era of 'Middle Life' within the Phanerozoic Eon, commonly called the 'Age of Reptiles,' distinguished by dinosaurs, ammonites, early mammals, the first birds, and ending in a mass extinction.

Cenozoic Era

The current geologic era of 'Recent Life' in the Phanerozoic Eon, characterized by the rapid diversification of mammals, birds, flowering plants, primates, and the rise of humans.