16-3 Flashcards
What are beaches?
Deposits of sediment that run parallel to the shore
Beaches extend inland as far as waves deposit sediments.
What causes water to drop its sediment?
When waves slow down
This process is similar to what occurs at river deltas.
What materials can make up a beach?
Different materials including:
* Large pebbles
* Fine sand
Composition depends on resistant minerals.
Which minerals are commonly found in beach sand?
Common minerals include:
* Quartz: beach sand
* Basalt: black sands
* Olivine: green sand
* Coral and shells: white sands
What is the impact of waves on shorelines?
Waves constantly erode, transport, and deposit sediment
This leads to the development of many shoreline features.
How does calm weather affect wave action?
Minimal wave action
In contrast, storms produce high energy waves.
What happens to cracks and crevices in the shoreline due to wave activity?
Cracks are created as water is forced into them, compressing air
The expansion of air after the wave subsides dislodges rock fragments.
What is abrasion in the context of waves?
Waves move sediments back and forth, wearing away rocks
This constant motion rounds corners and breaks down rocks/seashells to sand-size particles.
What is wave refraction?
Waves refract (bend) as they reach shallow water, aligning nearly parallel to the shore
Wave energy is constricted against headlands, leading to erosion.
What is longshore current?
The wave comes in at an angle and comes out to create a longshore current
What is longshore drift?
As waves come into shore at an angle, water and sand move straight across the beach
This process carries sand grains along the beach.
What is a sandbar?
A long ridge of deposits on an underwater slope
Sandbars can form from longshore transport.
What are rip currents?
Rush of water flowing rapidly outward through a narrow opening
They form as sandbars trap water flowing along the shore.
what are steepshore zones?
they are eroded by waves that carry sediment to quieter water.
what are wave-cut cliffs and platforms?
Where shoreline has steep slope, softer rock is at the base and sometimes digs into the side of the hill and makes a sea cave. If it gets too narrow it may collapse and create a cliff.
what is a sea cave?
the waves are carving out the softer, less dense rock at the bottom leaving the harder rock to dig in the side of a hill.
what are sea arches?
Bending waves may bore a hole through the headland. The land over the top is the sea arch.
what are sea stacks?
waves may erode sea arch further and it becomes thinner, when arch collapses it leaves a pillar of rock called a sea stack
what is a spit?
beach that projects like a finger out into the water from longshore drift deposits.
If sediments never get out of the ocean but washed along the shore, a spit may be formed. Attached to shoreline
what is a baymouth bar?
from a spit that forms across a bay with weak ocean currents, sealing off bay from ocean creating a lagoon inside baymouth bar
what is a tombolo?
ridge of sand that connects an island to the mainland
what are barrier islands?
Sand ridge/bar rising high enough above sea level than wind picks it up and builds sand dune, trees/grass grows on it and becomes a barrier island.
how are barrier islands formed?
from a spit disconnected from the mainland or sand dune ridges separated from mainland by ocean level
what are sand dunes?
hills of windblown sand making beaches more stable and lessen erosion.
Strong roots of dune plants hold sand in place slowing erosion
what are protective structures and how are they a problem?
built to protect coast from erosion or to prevent movement of sand along a beach
Problems: increases amount of erosion farther down the beach
what is a groin and why is it built?
built wall of rocks/concete built outward from the beach, built to reduce erosion along a stretch of beach, sand piles up against groins which interrupts water/sand flow, maintains/widens beaches there are losing sand
what are breakwaters and why is it built?
built parallel to shore, shield, coast, protecting properties
Reduce energy of waves by reflecting force of unspent waves seaward
what are beach nourishments? what are the pros and cons?
artificially adding large quantities of sand to a beach system, attempts to stabilize sand without building protective structures.
pros: improves beach quality and storm protection
cons: expensive and could harm marine life
