ERTH2003 Lecture 3

What are the four geological ways to transport sediment?

Earth movement (landslides), water, wind, and ice.

What is mass wasting?

The movement of sediment downhill owing to gravity.

What is the difference between mass wasting and erosion?

Mass wasting is sediment movement due to gravity; erosion is sediment movement by a medium (water, air, ice).

What is laminar flow?

A flow regime where fluid particles move in straight lines parallel to each other.

What is turbulent flow?

A chaotic flow regime where fluid particles mix and move in irregular paths.

What is the Reynolds number?

A dimensionless number used to predict flow type, indicating whether flow is laminar (Re < 500) or turbulent (Re > 2000).

What is Bernoulli's principle?

A principle stating that faster fluid flow results in lower pressure, generating lift.

What is bed load?

Sediment that is transported along the bottom of a stream bed.

What is saltation?

The process where sediment grains are temporarily lifted and then dropped back down.

What is the difference between wash load and dissolved load?

Wash load consists of sediments suspended in the water; dissolved load consists of ions dissolved in water.

What factors determine whether sediment is transported or deposited?

The settling velocity of sediment compared to flow velocity.

What does the Holstrom diagram illustrate?

The relationship between grain size, flow velocity, and whether erosion, transport, or deposition occurs.

What is hydraulic equivalence?

The principle that different particle sizes and densities can behave the same regarding sediment deposition.

What is the competence of fluid flow?

The largest size of particle that a fluid can transport.

What are bed forms?

Small-scale topography formed by sediment transport and the balance between erosion, transport, and deposition.

What are the two main types of sedimentary structures?

Primary structures and diagenetic structures.

What is a turbidity current?

A rapid underwater landslide of sediment that mixes with water, resulting in a dense flow.

What type of flow behavior does liquefaction typically exhibit?

It behaves as a plastic material, becoming fluid when sufficient stress is applied.

What is graded bedding?

A sedimentary layer with a fining upward sequence, where larger particles are at the bottom and smaller particles are at the top.

What indicates the direction of fluid flow in sedimentary structures?

The angle and arrangement of cross beds, ripples, and sedimentary layers.

What happens to sediment as fluid flow slows down?

Larger particles settle first, creating a fining upward sequence.

What are anti-dunes?

Bed forms that migrate against the flow direction due to high flow velocities.

What is aeolian transport?

Sediment transport by wind.

How does glacial transport differ from fluid transport?

Glaciers behave plastically, carrying sediments mixed together, which results in poor sorting when they melt.

What causes sediment to be deposited?

Sediment is deposited when the flow velocity decreases, allowing particles to settle.

What is the role of vegetation in sediment transport?

Vegetation can anchor soil and reduce erosion, thus influencing sediment transport patterns.

What are alluvial fans?

Alluvial fans are cone-shaped deposits formed where a river meets a flat area, losing energy and dropping sediment.

How do sorting and sediment size affect sedimentary rocks?

Well-sorted sediments indicate consistent transport conditions, while poorly sorted sediments suggest varied energy levels during deposition.

What is the significance of fossil content in sedimentary rocks?

Fossils provide insights into past environments and can indicate the age of the rocks.

What do mud cracks indicate in sedimentary layers?

Mud cracks indicate drying and exposure of sediment after deposition, often in a semi-arid environment.

How do ripple marks form in sediment?

Ripple marks form as a result of water or wind action on sediment, creating small ridges.

What is the difference between primary and secondary sedimentary structures?

Primary structures are formed during sediment deposition, while secondary structures result from post-depositional processes.

What is turbidity in sediment transport?

Turbidity refers to the cloudiness of a fluid caused by suspended particles, affecting light penetration and aquatic life.

What is the importance of sedimentary layers in geologic history?

Sedimentary layers record changes in environmental conditions and help reconstruct Earth's geological history.