Coastal Land Intrusion
A classroom/laboratory activity to use trigonometry to calculate how much the coastline has receded (and will recede in the future) because of sea level rise.
Continental Shelf
The gently sloping area adjoining the coast is called the Continental Shelf, where the average downward slope is only about 0.1o as shown in the graphic above.
- Use the figure provided above to explain how sea level rise results in large-scale inundation of the coastline.
- Use this depiction to explain to your students how trigonometric functions can be used to calculate the extent of land intrusion by the rising sea levels.
Recall the NASA estimate of sea level rise to be about 3cm in 10 years as noted from the previous tool. Now ask your students to calculate the coastline retreat because of sea level rise. Use the tangent trigonometric function to calculate coastline retreat.
Discuss how the coastline retreat is disproportionately large for what would seem like a very small vertical rise in sea level.
What could be the implications of rising sea levels on the coastal regions globally?
How much has the coastline approximately receded since the 1850s to the present times?
How much do we expect it to recede by 2100?
Answer key:
Sea levels have risen over 20 cm since 1850.
Sea level is expected to rise further by 30 – 120cm by 2100.
Video NASA’s Earth Minute: Sea Level Rise.