Earth's Tides Unit 7 Lesson 5 PDF

EARTH’S TIDES Unit 7 Lesson 5 Objective By the end of this lesson, you should be able to explain what tides are and what causes them in Earth’s oceans and to describe the variations in the tide...

EARTH’S TIDES Unit 7 Lesson 5 Objective By the end of this lesson, you should be able to explain what tides are and what causes them in Earth’s oceans and to describe the variations in the tides. Essential question What causes the Earth’s tides? What causes tides? Tides: daily changes in the level of ocean water caused by the difference in gravitational force of the sun and the moon across Earth. This is called tidal force. The moon is much closer to Earth than the sun, so therefore the tidal force is stronger. Therefore the moon is much more responsible for tides on Earth. LOW VS HIGH High tide: water level that is higher than the average sea level. Low tide: water level that is lower than the average sea level. As the moon moves around the Earth and the Earth rotates, the tidal bulges move around as a result. Tidal bulges follow the motion of the moon. As a result, most places on Earth have two high tides and two low tides each day.  tidal ranges Tides are due to tidal force. Tidal force: distance between the force of gravity on one side of the Earth and the other side of the Earth. Because the moon is closer to the Earth than the sun, the moons effect on the tides is twice as strong. The combination of the moon and the sun’s gravitational pull on Earth results in results in different tidal ranges. Tidal range: difference between the levels of ocean water at high tide and low tide. Also depends on the positions of the sun and moon relative to Earth.  tidal range Formula: high tide HEIGHT - Low Tide height  Spring tides: The largest tidal range Spring tides: tides that have the largest tidal range. These occur when the sun, moon and Earth form a straight line. The moon can be between the two or on the other side of Earth. Spring tides happen during a new moon and full moon phases, or every 14 days. Neap tides: The smallest tidal range Neap tides occur when the sun, Earth, and the moon form a 90 degree angle. During this, the gravitational effects of the sun and the moon on Earth do not add together as they do during spring tides. Neap tides occur halfway between spring tides, during first quarter and third quarter phases of the moon.  What causes tidal waves? The rotation of Earth and the moon’s revolution around Earth determine when tides occur. A place on Earth that is facing the moon takes 24 hours and 50 minutes to rotate to face the moon again. So the cycle of high tides and low tides at that place happens 50 minutes later each day. In many places there are two high tides and two low tides each day. Because the tide cycle occurs in 24 hour 50 minute intervals. it takes about 6 hours and 12.5 minutes for water in an area to go from high to low tide. It takes about 12 hours and 25 minutes to go from one high tide to the next.  Review What causes tides on Earth?  Review What is the difference between a spring tide and a neap tide?  Review Why is the timing of tides predictable?