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Sea Level Change
Exam 3
27
Geography
Undergraduate 1
05/02/2011

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Cards

Term
Eustatic sea-level change
Definition
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
Term
Isostatic sea-level change
Definition
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
Term
tsunami
Definition
 a large, often destructive, sea wave produced by a submarine earthquake, subsidence, or volcanic eruption. Sometimes incorrectly called a tidal wave
Term
tide gauge
Definition
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)
Term
barrier island roll over
Definition
sea level rise, pushing sand over the island
Term

barrier island migration: 

Definition

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.

Term
Lateral
Definition
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
Term
regressive
Definition
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.
Term
transgressive
Definition
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.
Term
barrier island drowning
Definition
barrier islands slowly being covered with water
Term
barrier island over step
Definition
beach rim around barrier island
Term
armor
Definition
armoring the shoreline against erosion; breakwaters, seawall, groins, tee groins, jetties
Term
beach replenishment
Definition
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
Term
Retreat
Definition
moving of houses and other foundations back when beach is eroding to quickly
Term
How low was world sea level at the time of the maximum glaciation? When was this?

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

1. raised marine mud
2. drowned deltas

3. raised shoreline
4. retreat of sea stacks

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

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

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

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

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

Definition
Relocate
Armor
Accommodate
Term

What is the downside to beach replenishment? 

Definition
very expensive and lasts only about 5 years
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