Geology Exam 3 Lecture 22

Front 1

The major factors that help to shape the world's coastlines:

Back 1

• Factors: sea level, waves, tides, wind, storms, hurricanes
• West coast – trench, active margins, narrow continental shelf, sea cliffs, rocky, bigger waves
• East Coast – wide continental shelf, passive margins, dunes, wide beaches, island

Front 2

The difference between an emergent and submergent coastline:

Back 2

Emergent coastline - coastlines that are rising relative to sea level
- Wave-cut notch above sea level
- Coral reefs exposed when sea level drops or land uplifted by tectonics
- Wave-cut platforms now marine terraces high above sea level
Submergent coastline - coastlines that are sinking relative to sea level
- Fjords: once glacier-carved valleys
- Coastal dunes may become barrier islands

Front 3

A few erosion and depositional coastline features:

Back 3

Erosion:
• Sea cliffs
• Caves and sea arches
• Pinnacles and sea stacks
• Wave-cut platforms
Deposition:
• Sandbar
• Spit
• Barrier island
• Baymouth bar

Front 4

How sea-level has changed over the past 18,000 years:

Back 4

Sea-level has been rising since the last glacial maximum

Front 5

The definition of wavelength, wave height, and wave steepness:

Back 5

The definition of wavelength, wave height, and wave steepness:
• Wave length – distance between the crests or two troughs
• Wave height – distance between trough and crest of wave
• Wave steepness – ratio of wave height to wave length

Front 6

How waves form and why they break:

Back 6

1. Wave slows once entering shallower water
2. Wavelength decreases
3. Wave height increases
4. Waves break once they become too steep

Front 7

How the beach profile changes seasonally:

Back 7

• Higher energy waves remove sand from the beach (winter)
• Lower energy waves return sand to the beach (summer)

Front 8

The process of longshore transport:

Back 8

• Waves approach shores at an angle
• Results in moving sediments along the beach

Front 9

The definition of a barrier island, how they form, and how they evolve:

Back 9

-Sand offshore that rises above high-water level comes
-Temporary
- Move landward as sealevel rises
-Storms cut new channels

Front 10

The three main types of 'solutions' to the beach erosion problem and problems associated with each of these 'solutions’:

Back 10

1. Sea Walls – hard structures to prevent erosion, do nothing to help our beaches, do the opposite of what they are supposed to so they cause more erosion of the beach
2. Beach nourishment – adding sand to the beach
3. Move away from the coastline

Front 11

Groins

Back 11

designed to catch sand that would otherwise travel further down the beach, like a wall = hard structure

Front 12

Jetty

Back 12

- designed to maintain permanent breach ways into harbors, bays, and lagoons, built to preserve channels = how they are different from groins

Front 13

Breakwaters

Back 13

designed to reduce wave energy on the shore to prevent erosion, a hard structure NOT built on the beach but in the water

Front 14

Seawalls

Back 14

designed to prevent buildings from falling in the ocean, seawalls always result in the loss of the beach

Front 15

Active continental margin

Back 15

a margin that coincides with a plate boundary and thus hosts many earthquakes

Front 16

Barrier island

Back 16

Barrier island – when offshore bars rise above the mean high-water level

Front 17

Beach drift

Back 17

Beach drift – the process where a sawtooth motion causes sand gradually to migrate along the beaches

Front 18

Beach face

Back 18

Beach face – a steeper, concave part of the foreshore zone, forms where the swash of the waves actively scours the sand

Front 19

Beach nourishment

Back 19

people working to increase the rate of sediment supply by trucking or shipping vast quantities of sand to replenish a beach

Front 20

Berms

Back 20

– horizontal to landward-sloping terraces that received sediment during a storm

Front 21

Coastal plain

Back 21

– a flatland that emerges with the continental shelf, as exists along the Gulf Coast and southeastern Atlantic coast of the United States

Front 22

Coastal wetland

Back 22

– a vegetated, flat-lying stretch of coast that floods with shallow water but does not feel the impact of strong waves

Front 23

Emergent coasts

Back 23

– where the land is rising or rose relative to sea level

Front 24

Estuary –

Back 24

where seawater and river water mix

Front 25

Eustatic sea-level change

Back 25

some relative sea-level changes are due to a global rise or fall of the ocean surface

Front 26

Fjord

Back 26

flooded glacial valleys

Front 27

Lagoon –

Back 27

a body of shallow seawater separated from the open ocean

Front 28

Longshore current

Back 28

– saw-tooth like flow which flows parallel to the beach

Front 29

Passive continental margin

Back 29

– margins that are not plate boundaries and thus lack seismicity

Front 30

Rogue wave

Back 30

– waves that are more than twice the size of most large waves passing a locality during a specified time interval

Front 31

Sandspit

Back 31

where the coastline indents landward, beach drift stretches beaches out into open water

Front 32

Submergent coasts

Back 32

coasts at which the land sinks relative to sea level

Front 33

Tide

Back 33

vertical movement/rise and fall of sea level

Front 34

Wave base

Back 34

- where there is increasing depth, the diameter still increases until, at a depth equal to about half the “wavelength”, there is no wave movement at all

Front 35

Wave refraction

Back 35

– waves bend as they approach the shore after making a large angle with the shoreline as they’re coming in