Coastal Geology and Sediment Dynamics

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Questions and Answers

What geological feature is formed when the arch of a coastal rock structure collapses?

Spit

Cliff

Stack (correct)

Bay

Which process primarily leads to the formation of a beach?

Underwater currents

Deposition by constructive waves (correct)

Glacial activity

Erosion by waves

What distinguishes a shingle beach from a sand beach?

Sand beaches are narrower and steeper.

Sand beaches have more vegetation.

Shingle beaches have larger particles and are steeper. (correct)

Shingle beaches are wider and flatter.

Which of the following is NOT a characteristic of a beach?

Stacks Signup and view all the answers

How does a spit form?

By longshore drift depositing material across a river mouth Signup and view all the answers

What is the term for a spit that has a curved end?

Recurved spit Signup and view all the answers

Which coastal feature forms when spits join two headlands together?

Tombolo Signup and view all the answers

What usually forms in the area behind a spit?

Mudflats or saltmarshes Signup and view all the answers

What impact does sea level rise have on fresh water bodies near the coast?

It increases salinity, making the water unsuitable for many uses. Signup and view all the answers

Which coastal area experienced an increase in flooding events from 1995 to 2014?

Kings Point Signup and view all the answers

What percentage of Bangladesh's land would be lost with just a 0.3m rise in sea level?

6% Signup and view all the answers

What is a characteristic of low-energy coastlines?

They are protected by coral reefs or islands. Signup and view all the answers

Which of the following is NOT a consequence of coastal erosion?

Creation of wave-cut platforms Signup and view all the answers

What are raised beaches formed from?

Former wave-cut platforms that are now above current sea level Signup and view all the answers

What indicates a positive sediment budget at a coastline?

More sediment enters the coastal system than leaves. Signup and view all the answers

Which coastal area is projected to have the highest flood costs by 2050?

Guangzhou Signup and view all the answers

How are sediment cells characterized?

They have clear boundaries that allow for balanced erosion and deposition. Signup and view all the answers

What feature is formed when sea level rises and partially submerges river valleys?

Rias Signup and view all the answers

Which process involves the compression of air in cracks of cliffs by waves?

Hydraulic Action Signup and view all the answers

What happens during cavitation in coastal erosion?

Compressed air violently expands when waves recede. Signup and view all the answers

What happens to the coastal ecosystems as a result of increased storms and erosion?

They face significant damage and loss of habitat. Signup and view all the answers

Which of the following is NOT a way waves erode the coastline?

Transportation Signup and view all the answers

What contributes to the formation of estuaries in coastal systems?

Sea level rise flooding river valleys. Signup and view all the answers

What is a primary characteristic of abrasion in coastal erosion?

It involves rocks and sediment grinding against each other. Signup and view all the answers

What characterizes the depth of fjords compared to other coastal landforms?

They have very steep sides and can exceed 500 m in depth. Signup and view all the answers

Which statement about the processes affecting coastal landscapes is accurate?

Active and relict landforms can coexist within coastal landscapes. Signup and view all the answers

How are dalmatian coastlines formed?

Through flooding of low-lying areas parallel to the coast. Signup and view all the answers

What factors influence the selection of areas for coastal management?

The economic viability of protecting settlements. Signup and view all the answers

What impact can a change in coastal processes have on landforms?

It can shift a landscape from erosion-dominated to deposition-dominated. Signup and view all the answers

What is meant by 'relict landforms' in coastal landscapes?

Landforms that date back to a past geological period but are still affected by coastal processes. Signup and view all the answers

What depth can notable fjords like Sognefjorden reach?

Over 1000 m. Signup and view all the answers

How do coastal landscapes change over time?

Changes can occur both gradually over years and suddenly due to events like storms. Signup and view all the answers

What is a potential disadvantage of using gabions for coastal protection?

They are not very strong. Signup and view all the answers

Groynes are effective at trapping material transported by what process?

Longshore drift Signup and view all the answers

Which feature of breakwaters can also act as a pedestrian walkway?

The connection to land Signup and view all the answers

Why might the placement of a groyne be crucial?

It can lead to rapid erosion behind it. Signup and view all the answers

What is one ecological concern associated with breakwaters?

They can cause sediment build-up harming ecosystems. Signup and view all the answers

Tidal barriers are particularly useful for managing what natural phenomenon?

Storm surges Signup and view all the answers

Which of the following is a drawback of using groynes?

They only last for 50 years. Signup and view all the answers

What is the primary purpose of riprap in coastal management?

To absorb wave energy and reduce erosion. Signup and view all the answers

Study Notes

Coastal Dynamics

Low-energy coastlines are often shielded by coral reefs or islands, resulting in fewer wave impacts.
These coastlines feature salt marshes and tidal mudflats, where sediment accumulation exceeds erosion, promoting land growth.
Coastal sediment inputs arise from river sedimentation, sea level rise forming estuaries, cliff erosion, and marine organism shell degradation.
The sediment budget assesses sediment balance: a positive budget indicates land extension, while a negative budget shows coastline retreat.

Sediment Cells

The coastline is segmented into sediment cells, which balance erosion and deposition.
Sub-cells exist with specific material inputs and defined boundaries like headlands; theoretically, these operate as closed systems, but practical transfers may occur.

Erosion Processes

Erosion occurs through various mechanisms:
- Abrasion: Wave-transported materials grind against coastal structures.
- Hydraulic Action: Waves compress air in cliff cracks, expanding pressure causes rock breakage.
- Cavitation: The release of compressed air from waves further erodes rock.
- Wave Quarrying: The force of waves detaches rock pieces from cliffs.

Coastal Landforms

Beaches form from constructive wave action depositing sand or shingle.
- Shingle Beaches: Steep and narrow, composed of larger particles.
- Sand Beaches: Wide and flat, made from smaller particles.
- Distinctive beach features include:
  - Berms: Ridges marking the high-tide line.
  - Runnels: Sand grooves parallel to the shore.
  - Cusps: Crescent-shaped markings on mixed beaches.

Spits and Bars

Spits: Sand and shingle formations extending into the sea due to shifting coastal directions, with variations like simple, recurved, and compound spits.
Offshore Bars: Form as materials accumulate in shallow areas, sometimes creating lagoons behind.

Impacts of Climate Change

Increasing storm frequency and intensity heightens risks to coastal ecosystems and infrastructures.
Rising sea levels lead to severe flooding, exemplified by Kings Point, NY, experiencing doubling flood events within a decade.
Projected land loss includes significant areas in Bangladesh and the Maldives with minimal sea level rise.
Saltwater intrusion threatens freshwater resources and agricultural viability, necessitating increased flood protection funding.

Coastlines of Emergence

Sea level fall unveils new landforms:
- Raised Beaches: Higher-level beaches developed from sediment accumulation.
- Wave-Cut Platforms: Exposed surfaces from eroded former shorelines.
- Relict Cliffs: Vegetative recovery of formerly coastal cliffs.

Coastlines of Submergence

Sea level rise results in submerged landscapes:
- Rias: Partially submerged river valleys.
- Fjords: Drowned glacial valleys with steep cliffs.
- Dalmatian Coastlines: Parallel islands formed by rising sea levels flooding valleys.

Coastal Management Techniques

Coastal management aims to mitigate erosion and flooding impacts on populations and environments, often prioritizing urban areas for resource allocation.
Riprap: Large rocks placed along shores to absorb wave energy, economically viable but may restrict access.
Groynes: Structures installed to capture drifted materials, wider beaches offer better protection but can lead to downstream erosion.
Breakwaters: Built offshore to reduce wave energy and protect coastlines, but can incur ecological costs.
Tidal Barriers: Mechanisms across river estuaries prevent floodwaters during storms, enhancing community resilience.

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Description

Explore the dynamics of low-energy coastlines influenced by coral reefs and islands. This quiz covers sediment sources, deposition, and coastal erosion processes. Test your knowledge on how these factors shape coastal systems.