Coastlines
The Earth’s surface is 29% land and 71% water. Coastlines are the interfaces between land and water and can have a profound influence on life on land. In this section, we focus on different aspects of coastlines from sediment found at coastlines to the shape of coastlines. Let’s begin with an examination of the types of sediment found on coastlines.
Watch the short video below to see the various kinds of sediment that collect in coastal environments. Even though the video is specific to New Zealand, the main sources of the sediment and the coastal processes observed are the same across the world. (Note: Turn on Closed Captioning if needed.)
Exercise 1 – Coastal Sediment
Use the resources below to answer the following questions:
- Chapter 17 Shorelines – Physical Geology – 2nd Edition (opentextbc.ca)
- 12 Coastlines – An Introduction to Geology (opengeology.org)
- The above video
- What are the four sizes of sediment that are commonly observed in coastal environments?
- What are the sources of most sediment found in the coastal environments?
- Which processes in the rock cycle cause the sediment to deposit along the coastal environments?
- Which of the following processes moves sediment along the coastlines?
- What is the source of quartz sand found along the coastlines?
- What other types of sediment may be found on the coastlines?
- Which of the following sediment are expected to be found in the coastlines environments near Charleston?
Let’s consider the sand found along the coastlines. Watch the second video above and use the additional resource below to answer the following questions:
- What is the predominant composition of sand grains in most places around the world?
- What is the chemical formula of silica sand?
- Which of the following minerals is most resistant to weathering?
- Igneous and metamorphic rocks (containing quartz, feldspars, mica, and amphiboles) are the more common rocks on the eastern side of the Appalachian Mountains. If these rocks are the source of all coastal sediment, which mineral is most likely to be found along the US Atlantic coastlines?
- Sediment in all coastlines around the world is made of quartz. T/F
- Why do smaller-sized sediments deposit along coastlines?
- Where do sediment finer than sand (silt and clay) deposit relative to the coastlines?
The Shape of the Coastline
In addition to the sediment that is brought to the coastlines by streams, ocean waves play a crucial role in shaping coastlines. Watch this video to learn how ocean waves are formed and answer the following questions:
Exercise 2 – Shape of a Coastline
Use the resources below to answer the following questions:
- Chapter 17 Shorelines – Physical Geology – 2nd Edition (opentextbc.ca)
- 12 Coastlines – An Introduction to Geology (opengeology.org)
- Sand Grains from Around the World! (geology.com)
- The above video
- How are ocean waves created?
- What is the fetch?
- The size of the waves is directly related to the length of the fetch. T/F
- Big waves carry a significant amount of energy. T/F
- Match the constructive and destructive waves with the following events: Transport and deposition of sediment/ Erosion of sediment.
- Coastal storms create constructive waves. T/F
- Wave refraction causes erosion and deposition in different parts of an active coastline. Match rocky headlands and wide bay and beaches with erosional and depositional environments.
Erosion and Deposition at Coastlines
First, let’s examine some of the main erosional features caused by ocean waves as shown in the video below.
Exercise 3 – Coastal Erosion
Use the resources below to answer the following questions:
- Chapter 17 Shorelines – Physical Geology – 2nd Edition (opentextbc.ca)
- 12 Coastlines – An Introduction to Geology (opengeology.org)
- The above video
- When wave energy is high coastal erosion takes place. T/F
- Of the following rock types, which rock types are more readily eroded by ocean waves?
- Differential erosion is referring to the erosion of coastlines with mixed geology that results in erosion in parts of the same coastline and deposition in another. T/F
- What is the ocean wave phenomenon that creates this differential erosion?
- Examples of coastal erosion at headlands include the following:
- The following processes were identified in coastal erosion of headlands:
Exercise 4 – Coastal Deposition
Use the resources below to answer the following questions:
- Chapter 17 Shorelines – Physical Geology – 2nd Edition (opentextbc.ca)
- 12 Coastlines – An Introduction to Geology (opengeology.org)
- The above video
- Deposition occurs when waves, streams, and wind loses energy. T/F
- Identify the depositional features along coastlines.
- Sediment deposited on beaches can include the following.
- In temperate zones (above the Tropics), winter storms tend to generate constructive waves. T/F
- Sediment that is moved along the beach in a sawtooth pattern by waves approaching the coastline at an angle is called longshore drift. T/F
Submergent and Emergent Coastlines
In addition to streams, wind, ocean waves, and the geology of the coastline, sea-level rise impacts the shape of the coastlines. Watch this quick animation before answering some basic questions:
Exercise 5 – Submergent and Emergent Coastlines
Use the resources below to answer the following questions:
- 17.4 Sea-Level Change – Physical Geology – 2nd Edition (opentextbc.ca)
- 12 Coastlines – An Introduction to Geology (opengeology.org)
- The above video
- What causes long-term sea-level changes?
- What is a submergent shoreline?
- What are some features of a submergent shoreline?
- What is an emergent shoreline?
- What are some features of an emergent shoreline?
