Chapter 10, Section 2Standards 3e. Students know there are two kinds of volcanoes; one kind with violent eruptions producing steep slopes and the other with voluminous lava flows producing gentle slopes.

Objective 1 Explain how the composition of magma affects the volcanic eruptions and lava flow.

Objective 2 Describe the 5 major types of pyroclastic material.

Objective 3 Identify the 3 main types of volcanic cones.

Objective 4 Describe how a caldera forms.

Objective 5 List 3 events that may signal a volcanic eruption.

Assessment Chapter Test

Review Daily Bellwork, Science Starters, Standards Practice

Chapter 13, Section 2

Key TermsCreate a flashcard for each of the following terms (found on p.325 in your text book).MaficFelsicPyroclastic MaterialCaldera

If you finish early, study your flashcards!

Key Terms

Volcanism

Any activity where magma rises to the crust is called VOLCANISM.

Volcanism occurs at mid-ocean ridges, subduction zones, and hot spots.

Viscosity

Viscosity= resistance to flowHigh Viscosity= honey, syrupLow Viscosity= water, sodaHigh Viscosity = more violent eruptions

Low Viscosity = quieter, more flowing eruptions

Types of Eruptions

Quiet Lava Flows

Explosive

Quiet Eruptions Usually oceanic volcanoes (Hawaii) Gentle Slopes Mafic Magma, low viscosity

Lava Flows

When mafic lava cools quickly, a crust forms on the surface of the flow.

The crust wrinkles and forms PAHOEHOE=“ropy”

If the lava is more viscous it cools and forms sharp and jagged rock = Aa.

If the lava has a high silica content if cools into blocky lava rock.

Explosive Eruptions

Felsic lavas (Mt.St.Helens) contain large amounts of trapped gases

When the volcano erupts the trapped gases escape and send lava and solid particles shooting into the air.

PYROCLASTIC MATERIAL= fragments of rock that form during a volcanic eruption

Steep Slopes

Types of Volcanoes

Shield• Broad

cones• Gentle

sloping sides

• Lava flows

Cinder• Steep

Slopes• Explosive

eruptions

Composite• Alternating

layers of lava flows and explosive eruptions

• Also called Stratovolcanoes

• Large Mountains

Caldera

When the magma chamber empties, the volcanic cone may collapse and leave a large “hole” or CALDERA

Volcanoes with very large eruptions can also cause a CALDERA

Many CALDERAS later fill with water and become lakes.

Brainpop-Volcano

INTERACTIVE/Assessment Create a 2-flap book Label each flap with the following:

Quiet Eruptions Explosive Eruptions

For each include Picture Description/Definition (2 sentences)