Science Seminar: Earth Science

The side of earth that faces the moon experiences a larger gravitational pull, due to the moon's closer proximity, than other parts of earth. This force causes earth itself to bulge slightly toward the moon. This bulge is termed an earth tide. Since water is free to move horizontally, the oceans tend to flow over earth's surface and collect in a secondary bulge on top of the earth tide; this water bulge is termed an ocean tide.

The new results show that sea level does not increase uniformly across the globe in response to melting of the polar ice sheets. In fact, sea level changes in response to ice loss are highly spatially variable, especially close to the retreating ice sheets. The new results, which are obtained with a numerical model of the global tides, show that the tidal changes due to ice sheet collapse and associated sea level changes will be highly variable and affect a number of different important processes.

Tide-generating forces are a result of the gravitational attraction between the Earth, sun, and moon

Tidal generating forces are based on the gravitational attractive force. While gravitational attractive forces vary inversely to the square of the distance between the objects, tidal generating forces vary inversely as the cube of the distance of the tide generating object.

New calculations suggest that, around 400 million years ago, many coastlines experienced two-week tidal cycles that varied in height by four metres or more. Such a huge range could have stranded fish in tidal pools for a couple of weeks. Only the ones with fins strong enough to muscle themselves out would have been able to journey back into the ocean and survive. Fossil evidence for the earliest known land vertebrates comes from places that had such wide tidal ranges.
15 FEBRUARY 2018

The moon and sun’s pull causes two bulges or high tides in the ocean on opposite sides of the earth.