# Mountains,volcanoes, and earthquakes

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Mountains,volcanoes, and earthquakes
Chapter C-1 Lesson 2 Mountains,volcanoes, and earthquakes

Earth’s interior The earth is not a solid ball of rock. Instead, it has three distinct layers: The crust The mantle The core

The Crust The crust is the outer layer, and is made of rock.
It is very thin compared to the other layers. If the Earth was an egg, the crust would be thinner than the egg’s shell.

The Mantle The layer of rock beneath the Earth’s crust.
Just under the crust, the mantle is solid. But the mantle is very hot, and the deeper you go, it gets like melted candy. We only see this when it comes to the surface through volcanoes.

The Core The core is the center layer of the Earth.
It is the hottest layer, and is divided into 2 parts: An outer core of molten or liquid iron. An inner core of solid iron.

Three Layers of the Earth
Crust Mantle Core Outer core Inner core

Earth’s crust moves The surface of the earth is not one solid piece. It is made up of many floating plates. Def : Plates: are rigid blocks of crust and upper mantle rock. Most of N. America, Greenland and the western half of the North Atlantic Ocean are on the North American Plate.

Earth’s Crust Moves Part of California and most of the Pacific Ocean make up the Pacific plate. There are 12 major plates in all, and they all fit together like a jigsaw puzzle. They float on the mantle’s soft rock. Plate movement is very slow, about a few centimeters each year.

Earth’s Crust Moves Each plate’s movement affects the surrounding plates.

Earth’s Crust Moves When plates collide, energy is released and new landforms are made. On land this is how mountains are made and volcanoes form.

Earth’s Crust Moves When plates pull apart, a rift or crack forms. These cracks are what we call valleys. Volcanoes can form above or under the oceans where plates pull apart. When plates pull apart under the sea, ridges form, and new sea floor develops.

Earth’s Crust Moves When plates slide and scrape past each other, they stick until they slide or slip. This is what we call earthquakes.

Earth’s Crust Moves This is a picture of the San Andreas fault line in California. It shows the crack that is forming in the crust.

Mountain formation Mountains form as the crust folds,cracks and bends due to plate movement. Many of the highest mountains form where two plates are colliding into each other. The “wrinkle” or mountains may form some distance away, not always right at the edge of where the plates bump into each other.

Mountain formation When plates pull apart, the gap allows magma to break through. Def : Magma: molten rock from the mantle layer. Magma builds up and forms long chains of mountains under the ocean mostly.

Volcanoes Volcanoes formed when molten magma exploded to the Earth’s surface. A volcano is a mountain formed of lava and ash. Def : lava- is magma that reaches the earth’s surface. Def : ash- small pieces of hardened lava.

Volcanoes Chains of volcanoes form when one plate is pushed underneath another plate.

Volcanoes The leading edge of the plate that is pushed under melts as it sinks into the mantle. The melted rock becomes magma that forces itself up between the plates. Sometimes volcanoes form in the middle of plates, over hot spots of magma. The magma melts a hole in the plate and rises up through the hole, causing an eruption. The Hawaiian islands formed this way. New islands are forming in this chain. Each island is a distinct result of how the lava and ash escape through the openings or vents of the volcano.

Earthquakes Def :earthquake- is a shaking of the ground caused by the sudden release of energy (a slip)in the earth’s crust. This energy comes from plates crushing together, scraping past, or bending along jagged lines of the plates. Earthquakes are very common, more than a million occur every year. Some are very strong,and some are barely felt by the inhabitants that live above them.

Earthquakes Many earthquakes occur along the Pacific Plate.
The earth’s crust can break apart, forming faults. Def :faults-places where pieces of the crust move apart.

Earthquakes Earthquakes send out energy in the form of seismic waves.
Def :seismic waves-are waves of energy traveling through the crust. They are like ripples that form on a pond when a stone is tossed in.

Questions to answer Describe three ways in which Earth’s plates interact. 1.push together 2.pull apart 3.slide past each other

Questions to Answer Q: What is magma and where does it come from?
A: magma is molten rock that comes from the lower mantle.

Questions to Answer Q: How do volcanoes form where oceanic and continental plates collide? A:the leading edge of the oceanic plate is pushed deep into the mantle where the rock melts and magma rises to the surface between the plates.

Questions to Answer Q: If one plate is pushing away from the plate next to it on one side, what must be happening to the boundary with another plate on the other side? A: The plate is colliding with the plate next to it on the opposite side.

Questions to Answer Q: Many strong earthquakes are caused by-
A:plates sliding past each other B:lava flowing down the side of a volcano C: plates spreading apart D: hot magma