Volcanoes, Sedimentary Rocks, and Weathering Flashcards

Flashcards covering the classification of magma and volcanoes, types of sedimentary rocks and their formation, transport mechanisms of sediment, various chemical and physical weathering processes, and groundwater characteristics.

Viscosity

The resistance to flow.

Silica content

The amount of Si and O within magma; low silica content equals low viscosity and more runny magma.

Gabbro

An intrusive rock that forms at mid-ocean ridges (MORs) where mafic magma crystallizes within the fractured crust and at depth below.

Andesitic magma

Magma with moderately explosive properties that builds steep-sided composite volcanoes, such as stratovolcanoes, typically generated at subduction zones.

Rhyolitic magma

Magma with the greatest explosivity that produces pyroclastic eruptions on an epic scale and forms caldera complexes above long-lived continental hot spots.

AA lava

Lava that forms chunks as it cools.

Pahoe lava

Lava where a crust forms on the surface while the inner layers remain runny.

Pacific Ring of Fire

A near-continuous chain of volcanic arcs and volcanic ranges, including island arcs and volcanic arcs.

Mount St. Helens

A volcano in the Cascade Island arc that had its last major eruption on May 18th 1980, resulting in 57 fatalities.

Crater Lake

A lake formed over 7,000 years ago when Mount Mazama erupted and the volcano’s tip collapsed into the drained magma chamber.

Clastic/detrital sediment

Solid pieces of preexisting rocks produced from weathering and erosion.

Chemical sediment

Sediment produced from chemical precipitates.

Biogenic sediment

Sediment produced from organic remains.

Chert

A chemical sedimentary rock composed of microcrystalline silica (quartz).

Oolitic limestone

A chemical sedimentary rock formed from small particles being rolled by currents and waves and picked up by precipitated calcite.

Micrite

A chemical sedimentary rock dark in color and formed of microscopic calcite.

Chalk

A biogenic sedimentary rock composed of the tests of microscopic plankton called coccolithophorids.

Coquina

A biogenic sedimentary rock composed of broken shells.

Coal

Accumulated organic material compressed under intense heat and pressure from peat bogs and swamps.

Lithification

The process of compaction and cementation of sedimentary rock.

Matrix

Smaller grains, such as silt or clay, within clastic sedimentary rock.

Grain

Larger clasts, such as sand or gravel, within clastic sedimentary rock.

Porosity

The percentage of pore space within a rock or sediment that is filled with air or fluid.

Solution

A method of stream transport where dissolved materials are carried by the river.

Suspension

A method of stream transport where fine material and sediment, like clay, are carried by the river.

Traction

A method of stream transport where large boulders and pebbles are rolled along by the river bed.

Saltation

A method of stream transport where small stones, pebbles, and silt bounce along the river bed.

Mature sediment

Sediment that has underwent extensive transport and is well rounded and sorted.

Physical weathering

The mechanical breakdown of minerals and rocks without a change to their chemical composition.

Chemical Weathering

The chemical decomposition of minerals in rock by oxidation, dissolution, or hydrolysis.

Biological weathering

The disintegration of rock physically or chemically by living organisms.

Hydraulic action

The energetic force of moving water that erodes rock, exemplified by the formation of retreating sea cliffs.

Freeze-thaw

A physical weathering process where water expands in volume by $9\%$ when frozen, applying stress to fractures and widening them over time.

Talus

Cone-shaped accumulation of debris, such as at Moraine Lake, formed from rock fall material loosened by freeze-thaw cycles.

Pressure release

A process occurring as deeply buried rock is exhumed, where the decrease in weight from overlying rock (overburden) causes the rock below to expand and form joints.

Differential weathering

A phenomenon where some areas of rock are more prone to weathering while others are more resistant.

Oxidation

A chemical weathering process where iron-bearing minerals react to produce rust.

Dissolution

A chemical weathering process where rock is dissolved in weakly acid water, significant in areas of karst topography.

Hydrolysis

A chemical weathering process where water breaks down the chemicals in a rock, such as the conversion of orthoclase to kaolinite.

Strandplain

A transitional depositional environment consisting of beaches, divided into the foreshore and backshore.

Shoreface

A shallow marine environment that extends from the fairweather wave base to the low tide mark and is always submerged.

Turbidity currents

Currents that sweep down submarine canyons and deposit sand and mud in large submarine fans in deep marine environments.

Turbidite

A graded bed consisting of alternating layers of sand/mud and thin deep-sea clays found in the continental rise.

Syneresis cracks

Subaqueous shrinkage cracks that result from fluctuations in salinity, occurring at the mouth of deltas.

Water table

The surface that separates the groundwater zone, where pore spaces are filled with water, from the unsaturated zone above.

Permeability

The ability of a rock or sediment unit to transmit fluids.

Aquiclude

A rock or sediment layer with low permeability that restricts the flow of groundwater.

Confined aquifer

A deep aquifer lying below an aquiclude that is recharged from a distance rather than from directly above.