Unit 3 – Oceanography Section 3: Currents, Waves, and Tides Earth Science Mr. Margetan

Ocean Currents Surface Currents – Movement of water on the surface, primarily caused by winds

Ocean Currents Longshore Currents – Currents which run parallel to the shoreline due to energy released from waves

Ocean Currents Upwelling Currents – Occur when wind moves seawater at the surface and new water from below replaces it

Critical Thinking #1 How might upwelling currents be beneficial to life in the ocean? Explain.

Ocean Currents Deep Currents – Move slowly beneath surface, primarily caused by differing water densities

Critical Thinking #2 What processes might cause changes in density that form deep ocean currents?

Ocean Currents Global Conveyor Belt – A connected deep ocean current that circles the entire planet

Waves Waves – Up and down, circular movement of energy in water Caused primarily by wind Also, disturbances in the ocean, earthquakes

Critical Thinking #3 How are ocean waves similar to seismic waves? How are they different?

Factors Influencing Wave Size Strength of Wind – Speed wind is blowing Fetch – Distance wind is blowing Duration – Length wind is blowing

Parts of a Wave Crest – Highest point on a wave Trough – Lowest point on a wave Wavelength – Horizontal distance from crest to crest Wave Height – Vertical distance from crest to trough

How do Waves Break? Waves begin to change shape at a depth ½ its wavelength Waves break at a depth of 1.3x its wave height

Critical Thinking #4 Considering how waves break, how might the shape of the ocean floor influence the shape of waves?

Types of Breakers Surging Breakers – Waves roll into the shore, occurs at steep beaches Plunging Breakers – Waves curl and break, occurs at moderate slope beaches Spilling Breakers – Waves break far from shore, occurs at gentle slope beaches

Tides Tides – Daily changes in the level of the ocean surface 2 high tides and 2 low tides each day caused by gravitational pull of primarily the moon, but also the sun

High Tides and Low Tides High (Flood) Tides – Occur on side of Earth facing and opposite the moon, due to both gravity facing and centrifugal force opposite Low (Ebb) Tides – Occur on sides halfway between the moon

Spring Tides and Neap Tides Spring Tides = Highest and lowest tides, when moon and sun align Neap Tides = Small tidal range, when moon and sun are perpendicular

Critical Thinking #5 Why are spring tides stronger than neap tides? Explain.