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)