1. Characteristics of Magma
Hotter Magma=More Fluid
More silica=Thicker
More dissolved gas = more explosive
Silica is formed from oxygen and silicon and is one of the most abundant materials in Earth’s crust and mantle.

2. Mr. Magner DHSHS Earth ScienceWords

3. Characteristics of Magma
Lava that is rich in Silica forms pumice and obsidian when cooled

4. Characteristics of Magma
Lava that is low in Silica forms basalt when cooled

5. Write your questions: Level 1 Level 2 Define compare Describe Contrast
Identify Group
List Sequence
Name Explain Classify/Categorize
Give the relationship
Cause/Effect
1 “Level 1” Questions & 1 “Level 2” Questions

6. Types of
Volcanic
Eruptions

8. Types of Volcanic Eruptions
The silica, and water vapor content of magma helps to determine whether the volcanic eruption is quiet or explosive.

9. Quiet Eruptions A volcano erupts quietly if it s magma flows easily
The gas dissolved in the magma bubbles out gently
Thin, runny lava oozes quietly from the vent
Produce two different types of lava: Pahoehoe and aa

10. Pahoehoe
HOT, FLUID lava, low in silica and extremely hot (around ºF).
Means “ropey”, due to its appearance.

11. Pahoehoe

12. Pahoehoe

13. Aa is cooler and slower-moving and forms rough surface consisting of jagged lava chunks

14. Aa

15. Aa

16. Shield Volcanoes Mr. Magner DHSHS Earth ScienceWords
Repeated lava flows during quiet eruptions gradually build up a broad, gently sloping volcanic mountain
Can rise from hot spot on the ocean floor like the Hawaiian Islands
Mr. Magner DHSHS Earth ScienceWords

18. Shield Volcanoes

20. Explosive Eruptions
If it’s magma is thick and sticky, a volcano erupts explosively.
It plugs the pipe like a cork in a bottle.
Gasses build up pressure and they explode.If its magma is thick and sticky, a volcano erupts explosively
It plugs the pipe like a cork in a bottle
Gases build up pressure until they explode
its magma is thick and sticky, a volcano erupts explosively

21. Ash

22. Ash

24. Ash

25. Explosive Eruptions cont.
A pyroclastic flow occurs when an explosive eruption hurls out ash, cinders and bombs as well as gases
Ash – fine, rocky particles as small as a grain of sand
Cinders – pebble-sized particles
Bombs – anywhere from baseball to the size of a car

26. Cinders

27. Cinders

28. bombs

29. bombs

30. bombs

31. Pyroclastic Flow
Out-running Mt. Pinotubo (Hopefully).