Ch. 9: Physical Processes Vocabulary: landforms, mountain, hill, plateau, plain, plates, plate tectonics, erosion, weathering

The Ring of Fire The ring of Fire is a circle around the Pacific Ocean where 90% of the world’s earthquakes and volcanoes happen. Earthquakes and volcanoes are two of the ways that the Earth changes under our feet, but there are many more.

Earth’s Surface Water covers 75% of the Earth’s surface. The other 25% is covered by land. Land is broken into pieces called landforms. There are many different types of landforms that make up the surface of the Earth.

Landforms Mountains: Landforms that rise above sea level, that are broad at the base and narrow at the top.

Landforms Hills: These landforms are similar to mountains, but smaller, and have rounded tops

Landforms Plateaus: Landforms that are like mountains, and hills, but flat on top with at least one side having a steep slope.

Landforms Plains: a large area of flat, or gently rolling land.

Volcanoes, Earthquakes, and Shifting Plates Earth’s outer layer is the crust. The crust is broken into big pieces called plates. The plates float on top of the next layer of the Earth that is made of magma (liquid/soft rock). Since the plate move slowly most of the time, we can‘t see it happening and have named the theory plate tectonics.

Volcanoes, Earthquakes, and Shifting Plates Since the plates are floating they often run into each other. Where two plates meet it is called a fault line. This happens in three ways:

Ways Plates Interact Plates move toward each other, thickening the crust, and forming mountains.

Ways Plates Interact Plates move away from each other forming trenches.

Ways Plates Interact Plates push past each other.

When Plates Move Plates that push past each other usually slide smoothly, but occasionally they get caught on rocks far beneath the surface on the other plate. When this happens pressure builds up until the rocks slip, or the plate breaks them. After the plate is freed it moves very quickly and causes vibrations in the ground. We call those vibrations earthquakes. Earthquakes can cause a lot of damage to people and property.

When Plates Move When earthquakes happen underwater, they can cause a vibration to run through the water creating a large wave that is capable of flooding hundreds of acres. These waves are called tsunamis, or tidal waves.

When Plates Move Sometimes when plates rub against each other it weakens the rock in the plates, allowing magma to push up through to the surface of the Earth. When this happens the magma escaping to the surface is called an eruption. The magma above the surface of the Earth is now called lava. A new volcano is born. When volcanoes erupt more than lava is spewed out, volcanoes also throw out clouds of ash and poisonous gasses.

Erosion and Weathering Erosion is a process by which wind, ice and rain break down big rocks into tiny rocks, or soil. Weathering is the process where wind or water moves around rocks or soil. The Appalachian Mountains used to be as tall as the Rocky Mountains, when they were first formed, but erosion and weathering have made them smaller and more rounded. Appalachian Mountains Rocky Mountains

Questions about Chapter 9 How are new mountains made? What 3 things cause erosion? What do Earth’s plates float on? How much of the Earth is covered in water? What are the pieces that the crust of the Earth is broken into called? What 3 things do volcanoes spew when they erupt?