Sea Level Changes Flashcards
What is eustatic sea level change caused by?
Eustatic sea level change is caused by a change in volume of water in the sea, or by a change in the shape of the ocean base. The effects are always global.
What is isostatic sea level change caused by?
Isostatic sea level change is caused by vertical movements of the land relative to the sea. Any downward movement of the land causes sea level to rise locally, while uplift of land causes sea level to fall. The effects are always local.
How has sea level changed in the last 10,000 years.
At the last glacial maximum sea level was about 130m lower than present. As temperatures started to increase (about 12,000 years ago), ice sheets melted, and sea level rose rapidly. It reached its present level about 4000 years ago. Over the last 4000 years, sea level has fluctuated around its present value. Since about 1930, sea level has been rising.
How are raised beaches formed?
They are formed when the fall in sea level leaves beaches above the high tide mark. Over time, beach sediment becomes vegetated and develops into soil.
How are marine platforms formed?
Sea level fall also exposes wave cut platforms (marine platforms), leaving them raised above their former level.
How are rias formed?
Rias are formed where river valleys are partially submerged. Rias have a gentle long and cross profile. They’re wide and deep at their mouth, becoming narrower and shallower the further inland they reach.
How are fjords formed?
Fjords are drowned glacial valleys they’re relatively straight and narrow, with very steep sides. They have a shallow mouth caused by a raised bit of ground formed by deposition of material by the glacier.
What are Dalmatian coastlines?
In areas where valleys lie parallel to the coast, an increase in sea level can form a Dalmatian coastline. Valleys are flooded, leaving islands parallel to the coastline.
What impact will sea level rise have on coastal areas?
- More frequent and severe coastal flooding. Flooding of low lying areas has increased with sea level rise and will increase more with further rises.
- Submergence of low lying islands. Lots of low lying islands are at risk of disappearing.
- Changes in the coast line. As sea level rises the coast line changes, islands are created, and the area of land is decreased.
- Contamination of water sources and farm land. Salt water may enter bodies of fresh water, damaging eco-systems and making the water unsuitable for lots of uses. Salt water entering soils may damage crops and make land impossible to farm.
- Sea level rise will increase coastal erosion putting eco-systems, homes and businesses at risk.
