Practice Exam GLY103

Geological Basin

In an eroded basin, the youngest rock layers will be found at the center, surrounded by progressively older layers.

Geological Dome

In an eroded dome, the oldest rock layers will be exposed at the center, with progressively younger layers outward.

Water Table

The water table is the boundary that separates the unsaturated zone above from the saturated zone below.

Unsaturated Zone

In the unsaturated zone, the pore spaces in the rock and soil contain both air and water, and pore water pressure is less than atmospheric pressure.

Saturated Zone

In the saturated zone, all pore spaces are filled with water, and pore water pressure is equal to or greater than atmospheric pressure.

Dendritic Drainage Network

A dendritic drainage network is characterized by a tree-like branching pattern with streams flowing in various directions and joining larger streams at acute angles.

Trellis Drainage Network

A trellis drainage network consists of parallel main streams with short tributaries entering at nearly right angles.

Flooding Response of Dendritic Network

A dendritic network might experience more widespread flooding as runoff accumulates from numerous tributaries spread across a uniform landscape.

Flooding Response of Trellis Network

A trellis network, confined by the parallel ridges of resistant rock, might experience flooding concentrated along the main valleys.

Erosion in Meandering Stream

In a meandering stream, erosion predominantly occurs on the outer bends of the meanders where the water velocity is higher, leading to the formation of cut banks.

Deposition in Meandering Stream

Deposition occurs on the inner bends where the water velocity is lower, resulting in the formation of point bars.

River Delta Formation

A meandering stream has the potential to form a river delta at its terminus through the processes of erosion and deposition.

Meander Bends

The curves in a river that migrate over time due to erosion on the outside and deposition on the inside.

River Delta

A landform created at the mouth of a river where it meets a larger body of water, formed by the deposition of sediment.

Braided Streams

Multi-channel river systems characterized by multiple, actively shifting channels that are typically unvegetated, forming in high sediment load and steep gradient environments.

Anastomosing Streams

Multi-channel river systems consisting of multiple channels separated by stable, often vegetated islands, typically deeper and less prone to rapid shifts.

Fracture (Joint)

A planar or sub-planar discontinuity in a rock caused by a loss of cohesion due to stress, with little to no significant movement.

Fault

A type of fracture characterized by visible displacement or movement of rock blocks along the fracture plane.

Brittle Deformation

The fracturing of a rock when stress exceeds its strength, resulting in discontinuities like faults and joints.

Ductile Deformation

The flow or bending of a rock under stress without fracturing, associated with the formation of folds.

Sediment Load

The amount of sediment transported by a river, influencing the shape and growth of deltas.

Wave Action

The movement of water caused by waves, which can affect sediment deposition in river deltas.

Subsidence

The gradual sinking of land, which can influence delta formation.

Channel Gradient

The slope of a river channel, affecting the flow velocity and sediment transport.

Offset Rock Layers

Evidence indicating that a fracture is a fault, showing displacement of rock layers on either side.

Geological Markers

Features that indicate movement along a fracture, helping to classify it as a fault.

High Sediment Load

A condition leading to the formation of braided streams, where a river carries a large amount of sediment.

Stable Islands

Vegetated islands that separate channels in anastomosing streams, promoting stability.

Permanent Deformation

Deformation that is irreversible, such as that caused by brittle deformation.

Flow Under Stress

The behavior of rocks during ductile deformation, allowing bending without fracturing.

Environmental Conditions for Braided Streams

High sediment load, steep channel gradient, and easily erodible banks.

Environmental Conditions for Anastomosing Streams

Lower gradient and deposition of fine-grained sediment.

Significant Movement

The displacement that classifies a fracture as a fault rather than just a joint.

Permanent Deformation

Occurs through mechanisms like crystal slip and recrystallization.

Brittle Deformation

Primarily associated with faults, representing fractures with displacement.

Ductile Deformation

Primarily associated with folds, representing the bending of rock layers without significant fracturing.

Depth within the Earth

Plays a crucial role as pressure and temperature increase with depth.

Shallow Depths

Where pressures and temperatures are relatively low, rocks are more likely to undergo brittle deformation.

Greater Depths

Higher pressures confine the rock, and higher temperatures allow for easier plastic flow, making ductile deformation more prevalent.

Normal Faults

Dip-slip faults that occur in extensional tectonic settings; the hanging wall moves downward relative to the footwall due to tensional stress.

Graben

A down-dropped block formed by normal faults.

Horst

An uplifted block formed by normal faults.

Reverse Faults

Dip-slip faults that occur in compressional tectonic settings; the hanging wall moves upward relative to the footwall due to compressional stress.

Thrust Faults

A type of reverse fault characterized by a low angle of dip (less than 30 degrees), resulting in significant horizontal shortening and crustal thickening.

Strike-Slip Faults

Fractures where the movement is predominantly horizontal and parallel to the strike of the fault.

Transform Plate Boundary

Settings where strike-slip faults occur, with plates sliding past each other.

Offset Streams

Distinctive landforms created by strike-slip faults.

Linear Valleys

Distinctive landforms created by strike-slip faults.

Sag Ponds

Distinctive landforms created by strike-slip faults.

Grain Size of Igneous Rock

Directly related to the rate at which the molten rock (magma or lava) cooled.

Intrusive Igneous Rocks

Form from magma that cools slowly beneath the Earth's surface, resulting in a coarse-grained texture known as phaneritic.

Phaneritic Texture

Coarse-grained texture where crystals are visible to the naked eye.

Extrusive Igneous Rocks

Form from lava that cools rapidly at or near the Earth's surface, resulting in fine-grained or aphanitic textures.

Aphanitic Texture

Fine-grained texture where crystals are too small to see without magnification.

Glassy Texture

Formed from extremely rapid cooling, like obsidian, with virtually no crystals.

Porphyritic Textures

Indicate a two-stage cooling history with large crystals (phenocrysts) in a fine-grained groundmass.