Barrier Islands

Question 1

What are in-between barrier islands?

Answer 1

Tidal Inlets (have bidirectional flow)

Question 2

What are the major components that drive the morphology of barrier islands?

Answer 2

1. Wave (more so)
2. Tides

Question 3

Draw and describe a wave-dominated barrier island system.

Answer 3

• Strong longshore currents
• Long skinny barrier islands.
• Influence of tides through the inlet will be much less (likely not going to have an ebb tidal delta but may have a small flood tidal delta)

example – outerbanks

Question 4

Draw and describe a mixed energy barrier island system

Answer 4

• Barriers tend to be short and stubby
• A lot of tidal inlets
• Likely to have larger ebb tidal deltas
• Example : VA ESVA

Question 5

What are the three main ways barrier islands form?

Answer 5

1. Offshore Shole
2. Beach that formed on the mainland
3. Spit building

Question 6

Barrier Island Formation: Draw offshore shole

Answer 6

Question 7

Barrier Island Formation: Mainland Detachment

Answer 7

• Beach that formed on the mainland.
• Sea level rises and so it is no longer attached to shore as a beach

Question 8

Barrier Island Formation: Spit Accretion

Answer 8

Question 9

Draw and describe longshore transport

Answer 9

• When a wave crashes on a beach, it does just come parallel to shore. It does crash parallel to the shore.
• As the waves crash onto the beach at an angle, gravity then pulls it back out.
• This repeats.

Question 10

The Bruun Rule

Answer 10

Associated with barrier island retreat (transgression) and the rate.

Question 11

How far does the shore retreat in 100 yrs?

B=3m / S= 5 mm/yr / L= 4km /h=7m

Answer 11

L = 4000 m

4000m/3m+7m = 4000/10 = 400x0.0005x100 = 200m in 100 years (2m/yr)

Question 12

Describe overwash

Answer 12

storm waves that crash over an island and deposit sand from the shoreface to the back-barrier

Question 13

What are the three processes that barrier island systems move?

Answer 13

1. Transgressive
2. Aggradational
3. Progradational

Question 14

Draw and describe a core sample of a transgressive migration of a barrier island system

Answer 14

Transgressive – generally when sea level is rising and we experience large storms.

Question 15

Draw and describe a core sample of a aggradational barrier island system

Answer 15

Would not have the same stratigraphy as transgressive

Aggradational – the island is accreting vertically (a lot of sediment supply and sea level is stable)

Question 16

Draw and describe a core sample of a progradational barrier island system

Answer 16