Water on the Move The Ebbs and Flows of the Sea
To use the Internet as a source for real and current data.
In most parts of the world, the difference between high and low tide amounts to only a few feet. Nevertheless, this change in water level still is enough to be very important in some areas. In many places at low tide, the water is too shallow to allow boats to move effectively into an out of harbors, whereas at high tide it is deep enough for them to do so. Because of their effect on navigation, tides have been studied for many years, and today physical oceanographers know quite a bit about their causes and characteristics.
You can also use our data and plot it with colored pencils on some graph paper:
Gather tide data for additional locations; try sites in Alaska and Hawaii. Compare the high tides for each of the locations. Look at maps for each of the areas and form a hypothesis for why these tides reach different heights.
Tides are cyclical and closely follow the phases of the moon. During the new and full moons, the distance between the high and low tides increases, which means that high tides get higher and low tides get lower. Use your chart to predict when the new moon or full moon will occur. Check your predictions by looking up moon phase data for the month you plotted at the US Naval Observatory's moon illumination page.