The reefs are built by living organisms, primarily corals.
The corals contain green algae in their interiors that provide oxygen the corals need to live.
Just think of the height of the coral as the distance travelled and the rate of coral growth as the speed.
This reef was thoroughly investigated by deep core drillings in preparation for its use as a test-site for a hydrogen bomb explosion.
This atoll is roughly circular with all the standard characteristics of a growing reef.
Nor have we taken into account the time necessary to form the volcanic base on which the reef grew.
Recently, further calculations for the rate of reef growth have been based on the concentration of dissolved calcium carbonate in seawater and upon the rate at which corals can absorb it and manufacture their shells.
These unconformities contain pollen from seed-bearing shrubs and trees, which indicates there were periods when the reef surface was above sea level (and so no coral growth at the surface) which lasted long enough for land plants to colonize the surface.
With this information we are ready to calculate the age of the Eniwetok reef.Using this value, the age of the reef is calculated by dividing 4,610 feet by 8 millimeters (about .3 inch) per year, which is about 175,000 years.But this is a minimum age since we have not taken into account the time periods (represented by the unconformities mentioned above) when the reef was not growing.The time is calculated by dividing the distance to be travelled by the speed or rate of travel.For example, if one is to travel 150 miles and one's average rate of speed is 50 miles per hour, then the trip will take 150/50 = 3 hours to make the trip, not allowing for stops along the way.During periods of volcanic inactivity, corals and lime-secreting algae colonize the areas just below the shoreline around the volcano.