1. Volcanoes

2. Volcano – opening in the earth where magma can rise to the surface
They can be:
Active – able to release magma and gases at any time
Dormant – do not release magma at any time currently
Extinct – no magma available

3. Parts of a Volcano
Magma chamber – collection of magma underground
Conduit – passage from chamber to vent
Crater/Central vent – opening at the top
Side vent – opening on the sides
Lava – magma above ground
Gases/Ash/Pyroclastic materials

7. Formation of Volcanoes
Rock underground is melted to form magma
Magma rises to the surface and exits the earth – process called volcanisms
On the surface it exists through vents - it is now called lava
The lava collects around the vent and sides of the opening

8. Largest concentration – at the Pacific Ring of Fire
Volcano Location
Most are at:
Divergent boundaries – at mid oceanic ridges
Convergent boundaries – at subduction zones
Rest are at:
Hot spots – thin areas of crust in the middle of the plate magma melts through
Largest concentration – at the Pacific Ring of Fire

9. Forming
Volcanoes

10. Volcanic
Island at
Hot Spots

12. Types of Magma
Magma has different consistencies based on what is in it
Malfic magma – rich in magnesium and iron
Dark, thin (low viscosity)
Felsic magma – rich in silicates
Light, thick (high viscosity)

13. Quiet Eruptions
Quiet - caused by thin magma with little gases
The lava gently flows out of the earth
Types of lava include:
Pahoehoe lava – lava that hardens smooth and ropey
Aa lava – lava that hardens with sharp edges

21. Violent Eruptions
Caused by thick magma with lots of gas
Releases gases, lava, and pyroclastic materials such as:
Volcanic ash – smallest pieces
Lapilli – small rocks that tend to fall near vent
Volcanic bombs – molten rock that starts to cool in the air
Volcanic blocks – pieces of the volcano that have broken off

32. Types of volcanoes
Shield – broad, gentle slopes, and made of lava
Gentle eruptions
Cinder – steep sides, made of pyroclastic materials
Violent eruptions
Composite – made of alternating layers of lava and pyroclastic materials
Both types of eruptions

33. Shield Volcano

34. Cinder Volcano

35. Composite Volcanoes

36. After an Eruptions
Volcano can form:
Crater – can fill with water to create a lake – called Crater lake
Caldera – depression formed when the sides of a volcano collapse into an empty magma chamber

42. What If Magma Stays Below Ground?
If cool enough - It can harden into igneous rock below ground – called plutons
Small horizontal – called sills
Small vertical – called dikes
Large collections – called batholiths

46. Predicting Volcanoes
Use signs like:
Increased earthquake activity – using seismometer
Bulges in the surface – as magma rises – using a geodiameter and tiltmeter
Increase in gases released
Changes in gas composition
Eruption history

47. Volcanoes – Are they good or bad?
Add carbon dioxide and water to atmosphere
Create new land
Add nutrients to environment
Bad:
Release poisonous gases
Destroy property and crops
Can create tidal waves and mudslides
Affect the weather