Sea Level Change

Eustatic sea-level change
global rising or falling of the ocean surface due to changes in either the volume of water in the world oceans or net changes in the volume of the ocean basins
Isostatic sea-level change
equilibrium in the earth’s crust such that the forces tending to elevate landmasses balance the forces tending to depress landmasses; ocean levels remaining calm and level
 a large, often destructive, sea wave produced by a submarine earthquake, subsidence, or volcanic eruption. Sometimes incorrectly called a tidal wave
tide gauge
An instrument that measures the alternate rising and falling of the waters of the ocean, and of bays, rivers, etc., connected therewith. The tide ebbs and flows twice in each lunar day, or the space of a little more than twenty-four hours (used for tsunami watch)
barrier island roll over
sea level rise, pushing sand over the island

barrier island migration: 

Barrier Island systems are not stagnant island but a system which is constantly changing and moving: three main types of island migration which are, lateral, prograding or regressive and transgressive.

When longshore transport has a directional flow established along the beach front of a barrier island it transports sand and other material along the beach. A consequence of this transport (as seen in the previous section with tidal inlet migration) is that material that once was up current is now deposited down current. This allows for the island to build on down current and is eroded on the up current side
systems which are ones that are prograding or building out into the ocean. Typically these systems are associated with a base level fall. So either there is a eustatic drop in sea level or a rise in continent level due to tectonic or sediment deposition.
system where the island migrates back towards the land. These systems are typically associated with a eustatic rise in sea level or continental subsidence. This process of migration has become very important in recent years as barrier islands have become populated. As these barrier islands migrate landward (a process which is happening all along the eastern seaboard of the US) people are losing property and homes to the ocean. In model B above it can be seen that the strata goes from fine grained lagoon sediments and becomes more coarse upwards. This is a result of the barrier island migrating over the top of the lagoon as it migrates landward.
barrier island drowning
barrier islands slowly being covered with water
barrier island over step
beach rim around barrier island
armoring the shoreline against erosion; breakwaters, seawall, groins, tee groins, jetties
beach replenishment
methods to restore beaches; a complementary term that describes a process by which sediment (usually sand) lost through longshore drift or erosion is replaced on a beach, restored naturally or artificially
moving of houses and other foundations back when beach is eroding to quickly
How low was world sea level at the time of the maximum glaciation? When was this?

120 m lower than today, 10,000 years ago
List four indicators of a higher-than-present sea level in Maine.

1. raised marine mud
2. drowned deltas

3. raised shoreline
4. retreat of sea stacks

What are the necessary characteristics of a seashell that is useful to construct a sea-level curve?
character of a helix, reservoir effect, clear definition of ridges in shell
How fast is modern, global sea level rising?
1.8 inches per year
Name the two factors causing modern sea level to rise?

1. glacial melting
2. tectonic activity
How do beaches survive rising sea level?
armoring (human activity): 
groins, breakwaters, seawall
or if they are just left they are usually drowned or washed over
How do we measure current rising sea level?

tide gauge
Suggest two plausible ways barrier islands might have formed?

1. spit detachment
2. mainland beach detachment and migration
Describe the stages of development of a beach resort: What marks the change from “exploration” to “development”?

1. involvement, development, consolidation
2. building and keeping beach at any cost
What three options do residents of an eroding beach have?


What is the downside to beach replenishment? 

very expensive and lasts only about 5 years

Leave a Reply

Your email address will not be published. Required fields are marked *