Tag: continental shelf

Are tides larger when the moon is instantly overhead?

Earth viewed from the surface of the moon

This NASA picture from the Apollo 8 mission exhibits the Earth seen over the horizon of the moon. Whereas the moon and solar trigger tides on our planet, the gravitational pull of those celestial our bodies doesn’t dictate when excessive or low tides happen.


Tides originate within the ocean and progress towards the coastlines, the place they seem because the common rise and fall of the ocean floor. Because of Sir Isaac Newton’s 1687 discovery, we all know that tides are very long-period waves that transfer by the ocean in response to forces exerted by the moon and solar. Nevertheless, these gravitational forces don’t management when excessive or low tide occasions happen. Different forces, extra regional than the moon or solar, management the tides. Lots of them need to do with the geography and form of the Earth.

The form of our planet has loads to do with variations in gravitational pull at numerous places. If Earth was a real sphere lined by an ocean of fixed depth, then it might be true {that a} excessive tide occasion would happen on the location with the moon overhead. The tidal “bulge” would transfer across the Earth with the moon, however this isn’t the case with our planet. The Earth just isn’t a real sphere, however bulges barely on the Equator. Additionally it is dotted with massive land lots (continents). Areas the place the Earth’s floor is larger, akin to mountains, have a stronger gravitational power than do locations the place the floor is decrease, akin to a valley or cavern. On the similar time, the depth of the world ocean varies vastly. All of those components play into the peak of the tides.

One other factor to think about when enthusiastic about tides is the dimension of time. There are lags in time when an observer experiences excessive or low tide, and the lag varies from one location to a different. For instance, the rising slope of the ocean ground approaching the U.S. East (often known as the continental rise, continental slope, and continental shelf) slows down the tidal “bulge” or “wave” of water. The lag may be hours and even near a complete day in some elements of the world. Consider the wave or bulge that you simply see if you throw a rock right into a pond. The wave travels outward in a hoop. If there’s a tree or different obstruction within the pond, the ring of waves would journey and wrap round it. The identical holds true for the tides.

NOAA’s Heart for Operational Oceanographic Merchandise and Providers makes use of superior acoustic and digital tools to measure and monitor the tides alongside our coasts. NOAA has water remark stations in additional than 3,000 places across the U.S. to look at water ranges and generate tidal predictions.

What’s a glass sponge?

a glass sponge

Probably the most well-known glass sponge is a species of Euplectella, proven right here within the northwestern Gulf of Mexico. Generally referred to as the “Venus flower basket,” this sponge builds its skeleton in a manner that entraps a sure species of crustacean inside for all times.


Glass sponges within the class Hexactinellida are animals generally discovered within the deep ocean. Their tissues include glass-like structural particles, referred to as spicules, which are made from silica (therefore their title). Some species of glass sponges produce extraordinarily massive spicules that fuse collectively in lovely patterns to kind a “glass home”—a fancy skeleton that always stays intact even after the sponge itself dies. The skeleton of the glass sponge, along with numerous chemical substances, gives protection in opposition to many predators. Nonetheless, some starfish are recognized to feed on these uncommon creatures of the deep.

Most glass sponges stay connected to laborious surfaces and eat small micro organism and plankton that they filter from the encompassing water. Their intricate skeletons present many different animals with a house.

Probably the most well-known glass sponge is a species of Euplectella, referred to as the “Venus flower basket,” which builds its skeleton in a manner that entraps a sure species of crustacean inside for all times. This sponge typically homes two small, shrimp-like Stenopodidea, a male and a feminine, who stay out their lives contained in the sponge. The crustaceans breed, and when their offspring are tiny, they escape to discover a new Venus flower basket of their very own. The pair contained in the basket clear it and, in return, the basket gives meals for the crustaceans by way of its waste. The animals finally develop too massive to flee the sponge, so they’re pressured to “keep put” for the remainder of their lives.