6-3 Volcanic Landforms

Volcanoes- Course 2

Vocabulary

Caldera- The large hole at the top of a volcano formed when the roof of a volcano’s magma chamber collapses.

Cinder cone- A steep, cone-shaped hill or small mountain made of volcanic ash, cinders,and bombs piled up around a volcano’s opening .

Composite volcano- A tall, cone shaped mountain in which layers of lava alternate with layers of ash and other volcanic materials.

Shield volcano- A wide, gently sloping mountain made of layers of lava and formed by quiet eruptions.

Vocabulary

Volcanic neck- a deposit of hardenedmagma in a volcano’s pipe

Dike- A slab of volcanic rock formed when magma forces itself across rocklayers.

Sill- A slab of volcanic rock formedwhen magma squeezes between layersof rock.

Batholith- A mass of rock formed whena large body of magma cools inside thecrust.

My Planet Diary pg.208BLOG

I was subjected to the sight of an active, dangerous volcano. We were on Hawaii, in a small aircraft over the Big Island. The volcano was quite large—maybe a few miles in diameter. Out of the top of this volcano, there was an immense pillar of smoke, being blown out to sea by the Hawaiian winds. Judging by the patterns of the hardened lava on the slopes of the volcano, it was a shield volcano. The whole area was literally oozing with volcanic activity. Quite a few large depressions had formed where presumably there had been a magma pocket that collapsed in on itself.

1.What landforms were created by the volcano that Jackson saw?

2.If you had the chance to visit Hawaii, would you prefer to see a volcano from an airplane or from the ground? Explain.

What Landforms do Lava and Ash Create? Pg. 209Volcanic eruptions create landforms made of lava, ash,

and other materials.

These landforms include:

shield volcanoes, cinder cone volcanoes, composite volcanoes, and lava plateaus.

Other landforms include calderas, which are the huge holes left by the collapse of volcanoes. Inside a caldera, a lake may form.

How a Caldera FormsA caldera is a hole left when a volcano

collapses. What is happening in the sequence of

diagrams?

Types of Volcanic Landforms pgs. 210-211

R. pg. 210-211

Volcanic MountainsLava from volcanoes cools and hardens to form lava

plateaus and three types of mountains.

Cinder Cone Volcanoes In an explosive eruption, ash, cinders, and bombs can build up around the vent in a steep, cone-shaped hill or small mountain that is called a cinder cone. A cinder cone volcano may be hundreds of meters tall.

Composite VolcanoesComposite volcanoes are tall, cone-shaped mountains in which

layers of lava alternate with layers of ash. Composite volcanoes can be more than 4,800 meters tall.

Shield VolcanoesThin layers of lava that pour out of a vent and harden on top of previous layers build a wide, gently sloping mountain called a

shield volcano.

Hot spot volcanoes on the ocean floor are usually shield volcanoes.

Lava Plateaus

Repeated floods of lava can form high, level plateaus called lava plateaus.

Fig. 2 Volcanic Landforms pg. 210

Use the graphic organizer to compare and contrast two types of volcanoes.

Assess Your Understanding pg. 211

1a. Review Volcanic landforms can be built up by

(lava only/ ash only/ both lava and ash).

b. Explain Suppose lava from a certain volcano has built up a steep, cone-shaped hill around a central vent. What can you conclude about the kind of lava that formed the volcano?

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I get it! Now I know that lava and ash can create the following landforms ___________________________________________

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APPLY IT! Pg. 211The Hawaiian Islands are very fertile, or able to support plant growth. In fact, many areas near volcanoes have rich, fertile soil. The rich soil forms after hard lava and ash break down. The ash releases substances that plants need to grow.1.Predict What type of industry might you expect to find on land near volcanoes?______________________________________

2.Analyze Costs and Benefits Lava flows could force people to flee their homes on the island of Hawaii. But in 2006, sales from crops on the island totaled over $153 million. Are the risks worth the rewards? Explain. _____________________________________________________________________________________________________________________________

What Landforms Does Magma Create? Pg. 212

Sometimes magma cools and hardens into rock before reaching the surface. Over time, forces such as flowing water, ice, or wind may strip away the layers above the hardened magma and expose it.

Features formed by magma include:

volcanic necks, dikes, sills, as well as dome mountains and batholiths.

Volcanic NecksA volcanic neck forms when magma hardens in a volcano’s pipe and the surrounding rock later wears away.

Dikes and SillsMagma that forces itself across rock layers hardens into a dike.

Magma that squeezes between horizontal rock layers hardens to form a sill.

Dome Mountains

A dome mountain forms when uplift pushes a large body of hardened magma toward the surface, which eventually becomes exposed.

Batholiths BatholithsBatholiths are common in the western United

States. A batholith is a mass of rock formed when a large body of magma cools inside the crust.

Assess Your Understanding pg. 213

a. Dikes and sills are two examples of landforms created when (magma / lava) forces its way through cracks in the upper crust.

b. What feature forms when magma cuts across rock layers?

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c. Which is older – a dike or the rock layers the dike cuts across? Explain.

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