Geology: Running Water, Crustal Deformation, Weathering, and Volcanoes

Practice vocabulary flashcards covering the hydrologic cycle, stream mechanics, weathering, soil, structural deformation, volcanic processes, and intrusive/extrusive igneous landforms.

Sheetflow

Water flowing downslope and overland as a film of water.

Stream Gradient

The elevation drop divided by distance along a stream channel.

Stream Discharge

The volume of water flowing past a given point at a given unit of time, typically expressed in cubic feet per minute.

Base Level

The lowest point to which a stream can erode, classified as either ultimate or temporary base level.

Alluvium

Sediments deposited by a stream, which tend to be well sorted.

Braided Stream

A stream consisting of broad, shallow channels that divide and rejoin, carrying large amounts of sand and gravel.

Meandering Stream

A stream consisting of a single sinuous channel characterized by cut banks, point bars, and oxbow lakes.

Narrow Valley

A valley formed by newly formed, downcutting V-shaped streams working to reach base level, often creating rapids and waterfalls.

Wide Valley

A valley formed when a stream is near base level and directs its energy side to side to erode laterally, creating meanders, oxbow lakes, and floodplains.

Mechanical Weathering

The physical breakdown of rocks into smaller pieces without changing their internal structure, driven by frost wedging, expansion, and biological activity.

Frost Wedging

The mechanical breakup of rock caused by the expansion of freezing water; considered the most important agent of mechanical weathering.

Chemical Weathering

The breakdown of rocks where the internal structure of minerals is altered, with water acting as the most important agent and clays and quartz as the primary products.

Soil

A combination of mineral and organic matter, water, and air.

Normal Fault

A dip-slip fault formed under tensional stress where the hanging wall moves downward relative to the footwall.

Reverse Fault

A dip-slip fault formed under compressional force where the hanging wall moves upward relative to the footwall.

Thrust Fault

A low-angle reverse fault resulting from compressional stress.

Accretionary Wedge

A geologic feature that forms between volcanic mountains and the shore at an ocean-continental convergent boundary.

Partial Melting

The process where mantle rocks melt first to form basaltic lava, becoming increasingly silica-rich as continental rocks are encountered and melted.

Caldera

A large steep-walled summit depression that sometimes forms when an underlying magma chamber cools and collapses.

Volcanic Vent

The pipeline through which magma rises to the surface during a volcanic eruption.

Island Arc

A chain of volcanic islands formed at an ocean-ocean subduction boundary from basaltic and andesitic lavas, exemplified by the Aleutian Islands and Tonga.

Magma Viscosity

A magma's resistance to flow, which decreases at higher temperatures and increases with higher silica content.

Shield Volcano

A large volcano built of low-viscosity basaltic lava producing large volumes of fluid lava that sometimes erupts from fissures.

Cinder Cone

A small, steep-sided volcano that typically forms in groups and is composed primarily of ash, dust, and larger pyroclastics ejected from a central vent.

Strata Volcano (Composite Volcano)

A volcano formed around the Ring of Fire from alternating flows of lava and ash, characterized by andesitic lava generated during ocean plate subduction.

Nuée Ardente

A high-speed eruption consisting of superheated gases combined with ash and pumice.

Dike

A sheetlike, discordant intrusive igneous body that cuts across pre-existing rock layers.

Sill

A sheetlike, concordant intrusive igneous body that forms parallel to existing sedimentary beds.

Batholith

The largest type of pluton, exceeding $100\,\text{square kms}$ in area, formed from massive bodies of magma that chill deep underground in place.