Why Do Ocean Tides Change?

Introduction

     If you’ve gone to the beach, do you ever wonder why the tides change? This website will tell you why.

Gravitational Pull

    The definition of a tide is the rise and fall of the oceans caused by gravitational pull of the Earth and Moon.  As the Moon rotates around the Earth, the gravitational pull develops the high and low tides.  

     The times for high and low tides change by 50 minutes each day because the Moon moves around the Earth and it’s not always in the same area at the same time each day. The tides are always changing throughout the day. 

     High tide and low tide happen when the gravitational pull of the Moon and the Earth work together to make the tides go up and down. When the Moon’s gravity pulls on the Earth, it causes water to bulge on the side closest to it. The bulge makes a high tide on both sides of the Earth.

Types of Tides

     In general, there are two tides in a day. Each tide has a high point and a low point. These tides are called high tide and low tide. A tide lasts half of a lunar day which is about 12 hours and 25 minutes.

     When the Earth, the Moon and the Sun are in line with each other a strong tide happens called a spring tide. These spring tides take place during a full Moon and new Moon phase.

     There are special tides that take place depending on specific phases of the Moon. A rare tide is a proxigean spring tide. This happens when the Moon is in between the Sun and the Earth, and the Moon is unusually close in the new Moon phase.  

     A neap tide happens during the quarter Moon phase.  This is a weak tide that takes place when gravitational forces pull the Earth from different directions and are perpendicular to the Moon and the Sun. 

    A storm tide pushes ocean water onto shore as the hurricane winds cause the tide to rise.

Tide Cycles

     When there is only one high and low tide, this is called a diurnal tide cycle.  When there are two high and low tides in a day, this is called a semi-diurnal cycle. When there are two high and low tides of different heights in a day, this is called a mixed tides.  

     Types of tides depend on the arrangement of land on Earth, the depth of the water at the coastline and the coastline’s shape.

Tidal Current 

     There are two types of currents, a flood current and an ebb current.  A flood current is a current coming in towards a high tide.  The ocean water flows from the ocean to the shore.  

    An ebb current is a current going out towards low tide.  The ocean water flows from the shore to the ocean.  When high tide or low tide is reached there is no current.  When this happens it is called slack water.

Hurricanes

     When storms like hurricanes come the tide level gets high and will likely result in greater chances of flooding.  A storm surge means there is an abnormal rise of the water made by a storm over a normal tide and is expressed in terms of height.  

     When a hurricane comes on shore the storm tide it makes causes damage to buildings, roads and bridges.  It also can cause harm to people.  Because the water rises so fast, it will flood and pose a risk to people to get hurt or drown.  

     Before a storm comes on shore scientists may use instruments to find out how strong a storm is by recording information about tides, waves and flooding.

Conclusion

    The next time you go to the beach you now know that the gravitational pull of the Earth and the Moon make tides change.