Download The Marine Environment

The Marine Environment
CH. 16
Shoreline Features
• Shorelines are shaped by waves, tides, & currents.
Erosional Landforms
• Water is a strong agent of erosion
• It acts greatest on rocky headlands, which occurs
through wave refraction.
– Wave Refraction is the bending of wave crests and
focusing them on the headlands.
Landforms Created By Wave Refraction
• Sea Stacks are created as weaker surrounding rocks
are broken and eroded away.
• Sea Arches are formed as strong rocks are undercut
by waves.
• Sea Caves form as breakers
erode into cliffs.
Beaches:
• Beach: A sloping band of sediment at the edge of
the sea.
• Composed of loose sediment deposited and eroded
by waves.
• Composition and color depends on parent material.
Estuaries:
• Estuary: Brackish water where a freshwater stream
meets the sea.
– Makes for great fish nurseries.
– Example: Chesapeake Bay
Longshore Currents:
• As you walk out to sea, the water gets deeper
and then shallow again.
– The deep part is called a longshore trough.
– The shallow region is a sand bar called the
longshore bar.
• This creates a channel of water that runs parallel to the
shore, called a longshore current
• Rip Tides form when water flows out to sea through
holes in the longshore bar.
– These are dangerous!!!
Depositional Features:
• Longshore currents form many features:
– Spit
– Baymouth bar
– Barrier Islands: Long ridges of sediment
deposited by longshore currents.
• These can connect with the mainland and form
peninsulas.
Changes in Sea Level
• Sea levels have been rising since the last ice age
ended.
• Effects of Sea Level Changes:
– Many coastal features will disappear if sea levels
continue to rise.
• There is a potential for sea levels to come up 70 m.
The Seafloor
Oceanic and Continental Crust
• As continents rise up from the ocean floor, a section
of them is covered by the water.
– Continental margins are the submerged parts of
continents.
• The continental margin is made of the continental shelf,
continental slope, and continental rise.
Continental Shelves
• Continental Shelf: The shallowest part of a
continental margin.
Continental Slopes
• After the continental shelf, the seafloor begins to
quickly drop.
– This is the Continental Slope
• The true edge of a continent.
• Erosion from the continental slope causes turbidity
currents, which cut canyons into the ocean floor.
– Deposits from a turbidity current for the continental
rise.
Ocean Basins
• The ocean basin is a deeper part of the seafloor
that lies above the oceanic crust.
– Basins are covered in pretty interesting topography.
Abyssal Plains:
• Plains covered in fine-grained sediments
• Deep Sea Trench: Depressions in the seafloor
Mid-Ocean Ridge:
• Mountain chains that run through ocean basins.
– Here, there are many volcanic eruptions and
earthquakes.
Hydrothermal Vents: Holes in the seafloor through
which water heated by magma flows.
Seafloor Volcanoes
• Most mountains on the ocean floor are extinct
volcanoes.
• 2 types:
– Seamounts: volcanoes more than 1 km high
– Guyots: volcanoes with flat tops.
Marine Sediments
• Most marine sediment comes from the continents.
– Tends to be fine-grained sediment called deep-sea mud.
• Ooze: Sediment containing a large percentage of
particles derived from once-living things.