Water falls:
Earthquakes, Volcanoes, and glaciers create waterfalls, too. They cause the land to shift. This changes the height in the bed of a river or a stream. With such a sudden change in height, a stream or river quickly becomes a waterfall. There are many types of waterfalls. Their names often describe how they look. Here are four: (1) Fan waterfalls fan out wide as they descend. (2) Block waterfalls descend in a wide sheet. (3) Tiered waterfalls drop in steps. (4) Punch bowl waterfalls fall into a wide, round pool.
Volcanoes:
But what is a volcano? Sixty miles (97 km) beneath our feet lies a layer of hot, half - molten rock called the mantel. Enormous crustal plates, thousands of miles across, float like rafts on this ocean of soft stone. The plates fit together like a giant puzzle. They push against one another or pull apart, moving so slowly that they might take a hundred years or more to travel an inch. In certain parts of the world, the movement of the crustal plates causes cracks to form deeper underground, all the way to the mantle. Molten rocks called magma fills the cracks, rising up through the crust towards the surface of the earth.
Glaciers:
Most glaciers look like soldi walls rising from the sea. Some have been around for thousands of years. Cold temperatures keep glaciers solid. But heat is a glacier's enemy. Rising temperature can break glaciers apart. In cold temperatures, the water molecules slow down. They bond together to form a solid mass of ice. But as temperatures rise, the molecules start to move around more, and they start to break their bond. The warm water under glaciers heats up. Melted water on its top also thins the glacier. This can cause a glacier to crack. If the crack is big enough an iceberg is born.
Caves:
Caves are natural openings in the earth. Some are holes in the side of mountains. Others go hundreds of feet down into the ground. Sea caves form on the coast and in the water. Caves have tunnels and rooms. These are called chambers. Tunnels connect the chambers and caves form in rock. Most caves are formed by erosion. And erosion is when something is worn down over time. Wind and water erode rock. Most caves form from water erosion. Caves in karst are the most common. Karst is land made up of limestone.
Rivers:
Usually a river begins as a stream in the mountains. Water from rain and snow adds to it, It trickles. It flows down a mountain. Many fresh tributaries feed it. A wider river forms. As a river flows, it carries sediment. It carries rocks and pebbles. The larger the material is called a river's load. The river's load erodes the channel. It makes it deeper. A river's channel is the path it takes across the land. The land at the river's edge is called the riverbank. Flowing water erodes the riverbank. The water gets wider. Soil, rocks, and plant life also affect the river's shape.
