Hurricanes, coastal zones, and processes

What factors impact coastlines?

• tectonic setting

• materials present at shore

• energy of water striking the coast

What is an active margin coast?

coastline associated with active plate tectonics, often cliffs

What is a passive margin coast?

coastline that is far from active plate tectonics, often with a broad shelf, beaches, and sandy offshore beaches

What are two signs of changing sea levels?

1. Emergent coastlines, seen by wave-cut platforms- as land uplifts, waves cut out new indents at the new sea level

2. submergent coastlines, seen by drowned valleys- large rivers drain water and sediments to form large deltas adjacent to coast (loading of crust and isolating an area of water can also form this)

What are the primary forces regulating natural shoreline modification?

Waves and Currents

How are breakers produced?

Water moves in circular motions in place as waves travel through- when the circular motion is no longer possible, waves collapse and breakers occur

How much energy do waves release?

wave energy is approximately equal to the square of the wave height- ex. a 2m wave releases and energy of 4

this is also dependent on local conditions of the coast, such as it’s steepness (a steeper beach will have a plunging breaker (high energy) while a gentle slope beach will have a spilling breaker (low energy))

How does the moon impact the tides?

Gravitational pull of the moon causes a bulge, generating high tide when closest to the moon and low tide when furthest away

What is the area exposed when the tide is out called?

Tidal flat

Define flood tide

the tide as it rises to its highest point

define ebb tide

the tide as it recedes to its lowest point

What are the three major parts of the beach?

Foreshore- where the water meets the shore

Backshore- where the high tide occasionally reaches

Dunes- the part of the shore that is not touched by water during normal tide changes

How does sand transport effect beaches?

Longshore currents erode sand and carry it further down the beach- the continued existence of a beach is dependent on continual supplies of sediment from the ocean or rivers

What does erosion around groins and jetties look like?

There will be sediment build up on the side of the obstacle that is being hit with waves, and severe erosion on the other side of the obstacle

What is the difference between storm surge and storm tides?

Storm surge- rise of water generated by a storm that is larger than predicted astronomical tides

Storm tide- rise in water level due to the combination of storm surge and astronomical  tide

What are the factors that impact a storm surge?

• wind

• forward speed of storm

• angle of approach to the coast

• central pressure

• shape of coastal features

• currents from the tide

What are the 6 conditions for a hurricane to develop?

1. Warm ocean water

2. distance from equator (coriolis effect needed for spinning, absent close to equator)

3. unstable atmosphere

4. low wind shear

5. High humidity

6. Tropical waves (typical beginning condition for hurricanes)

Are hurricans going to be more common in the future?

No, will be similarly common as most of the conditions needed to occur will not be effected, but will likely cause more damage/last longer, as oceans warm