- Slides: 21
What causes tides? • Tides are the daily rise and fall of Earth’s waters on its coastlines. • Tides are caused by the interaction of Earth, the moon, and the sun.
What causes tides? • The moon’s gravity pulls Earth’s water towards the moon. • This creates a Tidal bulge. • It also pulls the solid Earth slightly towards the moon. • This leaves water behind on the opposite side of the Earth.
What causes tides? • As Earth rotates, parts of Earth pass through these two tidal bulges. • When a location on Earth is at this bulge, it is considered high tide. • When a location on Earth is not in this bulge, it is considered low tide.
How often do tides occur? • High tides occur about every 12 hours and 25 minutes. • From high tide to low tide is about 6 hours and 12 minutes.
Different types of tides • A spring tide happens twice a month. • Occurs every full moon and new moon when the Earth, sun, and moon are aligned
Different types of tides • A neap tide happens twice a month as well • Occurs every 1 st quarter moon and 3 rd quarter moon when the Earth, moon, and sun form a right angle
Tides Video Clip
Quick Questions 1. Which is more dense, warm water or cold water? 2. If it is high tide a 3: 00 AM, when will the next high tide be? 3. If it is low tide at 5 PM, when will the next high tide be?
Currents And how currents effect climate
What is a current? A large stream of moving water that flows through the oceans
Surface Currents • What is a surface current? – A current that affects water to a depth of several hundred meters & is formed by the WIND!
How do they travel? • They flow in the direction of the winds. • The effect of Earth’s rotation on the direction of the winds and currents is called the Coriolis Effect. • VIDEO Hemisphere Currents Rotate Northern (us) Clockwise Southern Counterclockwise Arrow
Deep Currents • What are they? – Currents that creep slowly across the ocean floor and are formed by differences in DENSITY! – The density of water depends on its salinity and its temperature.
How does this work? • As temperature decreases and salinity increases, the water becomes denser and sinks. • Deep currents carry cold water from the poles back to the equator. • FYI: It may take as long as 1, 000 years to make the round trip from the pole to the equator and back.
How can currents affect climate? • Currents affect climate by moving cold and warm water around the globe and surface currents warm or cool the air above it, influencing the climate of the land near the coast.