TidesPresented to: Sir Mehtab AhmadPresented by: Group(A) Roll No 6151, 6152, 6153, 6154, 6155,

M.Sc Geography. 1st Semester

Contents• Definition

• Causes

• Theories

• Equilibrium Theory of Tides

• Dynamic Theory of Tides

• Types of Tides

• Effects of Tides

Definition• Tides are the cyclic rise and fall of sea levels

caused by the combined effects of the gravitational forces applied by the moon and the sun and the rotation of the Earth.

• One low-tide/high-tide cycle takes about 12 hours and 25 minutes.

Causes• The gravity of the moon and the rotation of the

earth causes the tides in Earth's oceans. The moon's gravity causes the ocean near to it to rise up and this rise up appears to sweep round the earth as the earth rotates.

Theories

Equilibrium Theory of Tides

• First developed by Newton stating that there is a bulge of water formed from the gravitational pull from the moon and centrifugal pull from the side opposing the moon. this explains most of the reasoning behind tides, but the main thing that it does not account for is that there are landmasses on earth that the bulge of water cannot move over.

Dynamic Theory of Tides

Types of Tides

• There are two major Types of Tides

• Spring TidesWhen the moon is full or new, the gravitational pull of the moon and sun are combined. At these times, the high tides are very high and the low tides are very low. This is known as a spring high tide. Spring tides are especially strong tides (they do not have anything to do with the season Spring). They occur when the Earth, the Sun, and the Moon are in a line. The gravitational forces of the Moon and the Sun both contribute to the tides. Spring tides occur during the full moon and the new moon. 

During the moon's quarter phases the sun and moon work at right angles, causing the bulges to cancel each other. The result is a smaller difference between high and low tides and is known as a neap tide. Neap tides are especially weak tides. They occur when the gravitational forces of the Moon and the Sun are perpendicular to one another (with respect to the Earth). Neap tides occur during quarter moons.

Neap Tides

Types of Tides

• Spring Tides

• Neap Tides