Sand and silt are both examples of granular materials, which are collections of separate particles and distinct particles, such as raw flour in a container or jellybeans in a jar.The most common forms of sand and silt are composed of tiny fragments of quartz.
Rip tides, also known as rip currents, are strong narrow currents that can pull swimmers out to sea. Some rip tides are so strong that they can drag swimmers away from shore before they realise what is happening. Swimmers should keep an eye out for rip tides while swimming in the sea at the beach. Rip tides can be identified by discoloured water, choppy waves and a foamy surface. They can be filled with debris. Swimmers are told to remember the âthree Rsâ if they become caught in a rip tide.
The incoming tide along the coast and into the bays and estuaries is called a flood current; the outgoing tide is called an ebb current. The strongest flood and ebb currents usually occur before or near the time of the high and low tides. The weakest currents occur between the flood and ebb currents and are called slack tides. In the open ocean tidal currents are relatively weak. Near estuary entrances, narrow straits and inlets, the speed of tidal currents can reach up to several kilometers per hour (Ross, D.A., 1995).