Idk if this sounds stupid but how dis beaches form? Did the earth just exist with a beach just like that or did sth cause beaches to form (with sand, shells, and stuff)
In: Earth Science
Over millions of years, wind, water, ice, the movement of the earth’s crust itself on the melted magma below, and even plants make rock crack into pebbles, pebbles ground into sand, sand ground into clay, and clay compress to rock. It is a large cycle.
Sand is moved by wind and water, and sometimes it accumulates for a while at the edge of the ocean, and we call it a beach. If the wind, rain and ocean currents change, the sand may be washed away and accumulate somewhere else and what was a beach becomes a rocky shore.
First, there are (generally) two kinds of beach sand: silica, and calcium carbonate.
Silica sand comes from the weathering of rocks – specifically, quartz which is silicon and oxygen. Quartz is very hard so it sticks around even as other bits often turn entirely to dust, or break off into big chunks that end up settling. The quartz bits get broken down into, well, sand and flow with rivers down towards the ocean. Rivers and streams are fast enough to pick up the relatively heavy silica bits and keep them moving. Once the water hits the ocean, though, it spreads out and slows down. Once it slows down, the heavy silica sand drops out until it gets picked up by waves.
Waves generally do the same thing that the rivers were doing, but in reverse. The tide comes in and waves pick up the silica sand and deposit it onto the beach, where it settles to the bottom. The tide recedes, leaving a beach. Wind will also pick up a lot of the sand and deposit it above the normal reach of the waves, where it gets captured by grasses growing in the dunes.
Calcium carbonate sand is also deposited by waves onto the beach, except calcium carbonate sand is made from ground up coral skeletons. Some of this is the result of powerful storms that break off pieces of corals and smash them around until the break up into tiny sandy bits. But a huge amount of that sand comes from parrot fish poop! Parrot fish are one of the few animals that can eat stony corals (the corals that have skeletons; not all corals do). Their teeth are fused together to form two powerful beak-like teeth that they use to bite off big chunks of coral, skeleton and all. Then, they use another set of teeth and jaws inside their throats, called pharyngeal jaws, to crush the coral down into bits, which they swallow. They digest all of the coral flesh and pass the skeleton bits in their poop. Those skeleton bits wash up with waves to form a beach.
Other kinds of minerals can be found on beaches, but it depends on the rocks and minerals found around that area. In general, even something like the black sand beaches are made the same way that a typical silica sand beach is made, except with something like volcanic basalt instead of quartz.
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