Chapter 15: Oceans

How much of the earth's surface is covered by the ocean?

70.8%

How fast are the winds of hurricanes?

119-300 km per hour. The force of the winds along with storm surge and heavy rains can destroy coastal areas.

Where do seamounts form?

Above hotspots

What is a gyre?

An ocean gyre is a large system of circular ocean currents formed by global wind patterns and forces created by Earth's rotation. The movement of the world's major ocean gyres helps drive the "ocean conveyor belt." The ocean conveyor belt circulates ocean water around the entire planet.

How does the lithosphere beneath a continent differ from that beneath an abyssal plain?

Due to isostasy, oceanic lithosphere rests on the asthenosphere so that its surface is lower than its surface is lower than the surface of continental lithosphere. Seafloor spreading stretches the lithosphere at the boundary between the ocean and continent and it gradually cools, gets denser, and sinks.

Where do abyssal plains develop?

On old, cool oceanic lithosphere.

What do wide continental shelves form?

Passive-margin basins

Why does sand on the beach move?

Sand moves with the swash and backwash of waves. If there is a longshore current, the sand gradually moves along the beach and may build spits

What does the landscape of the sea floor depend on?

The character of the underlying crust.

What are tides? How are they created?

The daily rise and fall of sea level - are caused by tide generating force. The largest contribution to this force comes from the gravitational pull from the moon.

What creates deep currents?

The vertical upwelling and downwelling of water. Some of this movement is thermohaline circulation.

What do humans do to protect beach property?

They build groins, jetties, breakwaters and seawalls.

Where do hurricanes form?

They form near the equator over warm ocean waters

What causes waves?

Waves are caused by friction where the wind shears across the surface of the ocean. Water particles follow a circular motion in a vertical plane as a wave passes. Waves refract (bend) when they approach the shore of frictional drag with the sea floor.

How do the shelf and slope of an active continental margin differ from those of a passive margin? Why do passive-margin basins exist?

active margin-narrow shelf and slope corresponds to the face of the accretionary prism(narrow shelf forms where apron of sediment spreads out over the top of an accretionary prism-the pile of material scraped off the downing subducting plate passive-bigger shelf

What is the Coriolis effect?

an effect whereby a mass moving in a rotating system experiences a force (the Coriolis force ) acting perpendicular to the direction of motion and to the axis of rotation. On the earth, the effect tends to deflect moving objects to the right in the northern hemisphere and to the left in the southern and is important in the formation of cyclonic weather systems.

Describe a beach profile

beach profile: cross section drawn perpendicular to the shore, illustrates the shape of a beach beginning from the sea and moving landward, a beach consists of a foreshore zone, or intertidal zone, across which the tide rises and falls. then the beach face, steeper, concave-up par of foreshore zone, forms where smash of waves scours the sand. the back shore zone extends from a small step to the front of the dunes or cliffs that lie farther inshore. the back shore zone includes one or more berms, horizontal to landward-sloping terraces that received sediment during a storm

What is an esturary? Why is it such a delicate ecosystem? What is the difference between an esturary and a fjord?

estuary: seawater and river water meet they are delicate because oceanic and fluvial water combine to make nutrient rick brackish water with salinity between oceans and rivers. they inhabit unique species of shrimp, clams, oysters, worms and fish that can tolerate large changes in salinity fjord: flooded glacial valleys

Discuss the different types of coastal wetlands. Describe the different kinds of reefs, and how a reef surrounding an oceanic island changes with time.

in temperate climates- swamps(wetlands dominated by trees), marshes(wetlands dominated by grasses) and bogs(wetlands dominated by moss and shrubs) tropical or semitropical-mangrove swamps reefs fringing reef: forms directly along coast barrier reef: develops offshore(separated from coast by lagoon) atoll: makes circular ring surrounding a lagoon eventually reef itself sinks too far below sea level to remain alive and it becomes the cap of a guyot

Where does the salt in the ocean come from? How do the salinity and temperature in the ocean vary?

most cations in sea salt come from general chemical weathering of rocks and the anions come from volcanic gases. rivers deliver over 2.5 billion tons of salt to the sea every year. salinity varies with location. it reflects the balance between the addition of freshwater by rivers or rain and the removal of freshwater by evaporation. it may also depend on water T bc warmer water can hold more salt general correlation of average T with latitude exists bc the intensity of solar radiation varies with latitude

What have humans done to the coats?

pollution; Coral reef bleaching

What factors control the direction of the surface currents in the ocean? Explain thermohaline circulation.

surface currents result from interaction between the sea surface and the wind and the rotation of the Earth. Coriolis effect: causes surface currents in the northern hemisphere to veer toward the R and surface currents in the southern hemisphere to veer toward the left of the average wind direction. it's caused by earth's rotation thermohaline circulation: rising and sinking of water driven by density contrasts caused by differences in T and salinity

How do plate tectonics, sea level changes, sediment supply, and climate change affect the shape of the coastline? What is the difference between submerging and emergent coasts?

tectonic setting of a coast plays a role in determining whether the coast has steep sided mtn slopes or a broad plain that borders the sea(active margin creates mtns and passive margin leads to broad coastal plain) emergent coast: land is rising and terraces form along some coasts submergent: land sinks relative to sea level causes estuaries and fjords erosional vs accretionary coasts warmer climate means weathering happens less quickly

What is the continental shelf? Where is it located?

the area of seabed around a large landmass where the sea is relatively shallow compared with the open ocean. The continental shelf is geologically part of the continental crust.

What is bathymetry?

the measurement of depth of water in oceans, seas, or lakes.

What are surface currents driven by?

the wind; are deflected by the Coriolis affect.

Describe how waves effect a rocky coast and how such coasts evolve

they don't have a beach so a breaker can pick up boulders and smash them together until they shatter and it can squeeze air into cracks making enough force to widen them. the shattering, wedging, and abrading(wave erosion) gradually undercut a cliff face and the cliff retreats if it becomes unstable enough and breaks away

What causes the tides? Why does tidal reach very with location?

tides are caused by the tide-generating force-due partly to the gravitational attraction of the Sun and Moon and partly to centrifugal force caused by the revolution of the Earth-Moon system around its center of mass. forces causing tides: gravitational pull, centrifugal force, earth-moon system, center of mass range and tide reach varies bc of tilt of Earth's axis, the moon's orbit, the sun's gravity, and the focusing effect of bays, basin shape, and air pressure

The salinity, temperature and density of seawater vary...

with location and depth

Describe the motion of water molecules in a wave. How does the beach sand migrate as a result of longshore drift?

within a deep ocean wave, water molecules follow a circular path and the radius of the circle decreases with depth. beneath the wave base, water modules are not affected by the wave. wave refraction occurs when waves approach the shore at an angle. if the wave reaches the beach at an angle, it causes a longshore current and beach drift of sand