Beaches and Barrier islands

Question 1

Berm

Answer 1

High point where beach slopes seaward and landward

Question 2

Longshore transport

Answer 2

River of sand moving along beach

Question 3

Why are barrier islands important?

Answer 3

-Protection from storms
-Take the wave energy
-Economy

Question 4

What is a barrier island?

Answer 4

Sandy, shore - parallel islands separated from the mainland by estuary, lagoon, or tidal environments

Question 5

Dunes

Answer 5

-Shore Parallel fine sand ridge
-Wind blown

Question 6

Beach ridges

Answer 6

-Shore parallel coarser sand ridge
-Due to changes in sed. Supply by storm waves, etc.

Question 7

Overwash fan

Answer 7

-Fan shaped sand
-Storm surges through dune low and spreads out on marsh

Question 8

Back barrier

Answer 8

-Marshes - intertidal vegetated flat
-Tidal creeks - muddy/ sandy channel

Question 9

Spits

Answer 9

-Longshore extensions of barrier islands
-Tells you direction of longshore current

Question 10

Tidal deltas

Answer 10

-Sandy shoals seaward (ebb) and landward (Flood) of an inlet
-Tides move through inlet; spread out and slow; deposits

Question 11

Inlets

Answer 11

-Narrow water passage between barrier islands
-Returning storm surge cuts channel

Question 12

Describe Wave-Dominated Barriers

Answer 12

-Long, narrow, low islands
-Few tidal inlets
-Small ebb tidal deltas
-Washover sand in common

Question 13

Why do wave dominated barriers have few inlets?

Answer 13

Longshore moves sand

Question 14

Describe Mixed Energy barriers

Answer 14

-Short, wide, higher islands
-Numerous large inlets; -Large ebb tidal deltas
-“ Drum stick” Shape
-Tides cause ebb tidal delta to extend seaward

Question 15

Drum-stick shape

Answer 15

1. Larger ebb deltas
2. Wave refraction over ebb delta
3. Local updrift reversal of alongshore current
4. beach ridges prograde

Question 16

Why is there no tide dominated barrier island?

Answer 16

Tides are perpendicular and barrier islands are shore-parallel

Question 17

Barrier island formation

Answer 17

1. Emerging bar (Traps sand)
2. Breached spit (Cut-through spit)
3. Drowned coastal storm ridge (rising sea level)

Question 18

How do barrier islands migrate landward during a sea-level rise?

Answer 18

Erosion of seaward, deposit sed, on landward

Question 19

Retrogradational/ Transgressive

Answer 19

Seaward over landward environments

Question 20

Progradational/ Regressive

Answer 20

Landward over seaward environment

Question 21

Why might most modern barrier islands have basal radiocarbon dates around 4000 ya?

Answer 21

Slowed sea level, sediments caught up
Switch from retrogradation to aggradation or progradation