Oceanography Study Guide

The Ocean Floor

• Abyssal Plain: The flattest place on Earth, located on the deep ocean floor and covered in thin sediments deposited by turbidity currents.
• Continental Rise: Deposition of sediments at the base of the continental slope. Absent at Active Continental Margins
• Continental Shelf: Part of the continent covered by water. Wide at passive margins, narrow at active margins.
• Continental Slope: The steeply sloping edge of the continent.
• Guyot: A seamount with a flat top, indicating it was once above sea level.
• Mid-Ocean Ridge: An underwater mountain chain where two tectonic plates are diverging, creating new crust.
• Rift Valley: The location of new oceanic crust formation.
• Seamount: An underwater mountain of volcanic origin.
• Trench: A deep, v-shaped valley in the ocean floor caused by subduction at convergent boundaries.

Ocean Currents

• Current: A continuous stream of water in the ocean.
• Surface Current: Shallow currents (top 100 m of ocean) caused by wind. They transport warm water from the equator to the poles and cold water from the poles back to the equator.
• Upwelling: Vertical movement of cold, dense water caused by surface winds blowing water away.
• Gyre: A circular loop of surface currents that spin clockwise in the Northern Hemisphere and counterclockwise in the Southern Hemisphere.
• Coriolis Effect: Deflection (turning) of moving objects (like winds and surface currents) caused by the Earth’s rotation.
• Deep Currents: Thermohaline circulation caused by differences in density (due to temperature and salinity). It mixes and exchanges water between the oceans.
• Gulf Stream: A warm current that affects the east coast of the United States.
• California Current: A cold current that affects the west coast of the United States.

Salinity

• Salinity: Measure of dissolved salts in water. The average ocean salinity is 35 ppt (parts per thousand).
  • Increase Salinity: Freezing and evaporation.
  • Decrease Salinity: Precipitation

Wave Size Factors

• Wind Speed: The speed at which the wind travels.
• Fetch: The uninterrupted distance the wind can blow without changing direction.
• Duration: The amount of time the wind blows.

Wave Anatomy

• Crest: (C) The peak of a wave.
• Trough: (B) The lowest part of the wave.
• Wavelength: (D) The distance between wave crests or troughs.
• Wave Height: (A) The distance between the crest and trough of a wave.

Special Waves

• Breaker: A wave that is affected by water depth, rising higher before crashing into the shore/beach.
• Tsunami: A long-wavelength wave caused by seafloor displacement, such as an earthquake, landslide, or underwater eruption.

Ocean Zones

• Surface Layer: Mixed layer where sunlight penetrates and waves and wind mix the layer.
• Thermocline: Layer where mixing stops and the temperature rapidly decreases.
• Deep Layer: The deep layer of the ocean, which is very cold and dark because sunlight cannot penetrate.

Tides

• Tides are caused by the gravitational pull of the sun and moon.

Continental Margins

• The Continental Margin is the transition between continental crust and ocean floor. They can occur either at a plate boundary or far away from a plate boundary and consist of a continental shelf and slope and may include a continental rise at certain locations.

Active Margins

• Occur on plate boundaries.
• Often have trenches, narrow continental shelves, no continental rises, and steep continental slopes.
• Earthquakes and volcanic mountain ranges may occur near active margins.

Passive Margins

• Occur far from plate boundaries.
• Often have wide continental shelves, continental rises, and gentle continental slopes.