1. Volcanoes

2. Craters Bowl-shaped geological formation @ top of volcano SP Crater
Flagstaff, Arizona

3. Calderas Formed by violent explosion that collapses into a depression*
Nearly circular
Size > 1 km diameter
Width ~ 5 miles
Average depth ft.
Crater Lake
Oregon

4. Olympus Mons, Mars

5. Santa Ana Volcano: El Salvador
Crater & Calderas

6. Plateau
Plateau formed by volcanic activity
Lava or
Pyroclastic

7. Volcanic Pipe (Necks)
Volcanic necks are resistant vents left standing after erosion has removed the volcanic cone
Ship Rock, New Mexico
Devil’s Tower, Wyoming

8. Volcanic Hazards: Lava Flows
Basaltic lava can travel from mph
Lava with higher % of silica will move slower

9. Volcanic Hazards: Pyroclastics
Rocks of variable sizes from 2 mm > 1 m
Ash to boulder size

10. Volcanic Hazards: Pyroclastic Flows
Nuée ardente – ash, hot gas, & volcanic fragments
Hot, > 1,000°C
Fast, > 250 km/hour

11. Volcanic Hazards: Lahars
Flow of mud, rock & water
Fast > km/hr
Destroys just about everything in its path.

12. Volcanic Hazards: Toxic Gases
90% of gas emitted is Water Vapor
Carbon dioxide (CO2),  Sulfur dioxide (SO2), Hydrogen sulfide (H2S),  methane (CH4), carbon monoxide (CO), fluorine (F).
Can result in Acid Rain
CO2 is heavier than “air”, get trapped & can suffocate people & animals.
Fluorine ingested by animals

14. Active Volcanoes @least 1 eruption < 10,000 yrs. ~1500 currently,
~500 within the last 3000 yrs. (written history)
Mt. St. Helens
Washington
Mt. Etna
Italy

15. Dormant Volcanoes
Dormant: active volcano that is not erupting, but could erupt again
Mt. Rainier (1894)
Mt. Fuji (1707)
Mauna Kea, Hawaii (~1000 BCE)

16. Extinct
last eruption > 10,000 years & not expected to erupt again (~79 MYA)
Pilot Knob
Austin, TX