Water flowing over Earths surface or underground causes erosion and deposition. Water flowing over a steeper slope moves faster and causes more erosion. How water transports particles depends on their size. When water slows down, it starts depositing sediment. This process starts with the largest particles first. Runoff erodes the land after a heavy rain. It picks up sediment. Runoff carries most of the sediment to bodies of water. Mountain streams erode narrow, V-shaped valleys and waterfalls. Erosion and deposition by slow-flowing rivers create broad floodplains and meanders. Deposition by streams and rivers may form alluvial fans and deltas. Floodwaters may deposit natural levees. Erosion and deposition by groundwater can form caves and sinkholes. Stalactites and stalagmites are mineral deposits. They build up in caves as water continues to drip.

What picks up sediment after a heavy rain?

You know that friction also causes heat. Think about when you rub your hands together. It is friction that makes them warm. But why does this happen? Friction causes the molecules on rubbing surfaces to move faster. Faster moving particles have more heat energy. Heat from friction can be useful. Can you think of other places where you might find friction? Friction also lets you light a match. Heat from friction can also cause problems. It can cause a car to overheat. To reduce friction, oil is added to the engine. Oil coats the surfaces of moving parts. This coating of oil makes them slippery. When things are slippery there is less friction. Have you ever seen a sign that says, slippery when wet? This too has to do with friction. Water, like oil, can reduce friction. The wet surface may allow your shoes to slide more easily.

What problem can friction cause?

After his cousin Joe dies , Layne Vassimer and his girlfriend Macy , along with their friends Stephen , Maurice , Iris and Katrina , decide to clean up Joe's house with the intention of selling it . When they see it for the first time , they discover the house completely covered in plates of iron armor . The group also finds crop circles in the nearby cornfield . When Iris , one of their friends , suddenly disappears they realize something is really wrong . During a blackout , the house is attacked by aliens , who had previously killed Joe and abducted Iris . The group figures out the aliens are allergic to iron , Joe had covered the house in it to keep them out . They attempt to fight the aliens off , but the house is eventually blown up with Layne , Macy , and Katrina the only survivors . In the end , they drive off , listening to the radio . They hear a news report stating that the blackout they experienced affects five western states and parts of Canada . They also hear that people everywhere are being attacked by '' strange creatures . ''
Who attacks the house following Iris's disappearance?