Volcanoes on Earth

1. Volcanoes on Earth How are volcanoes and their features created? USGS, SP crater, Arizona

2. How are volcanoes made? through cracks or faults in the crust and onto the surface as Lava and/or tephra Magma rises up from the mantle under pressure USGS

3. What are the major types of volcanoes? Shield Volcanoes Figures from USGS Stratovolcanoes (composite) Cinder Cones

4. flow crater cone of cinders CINDER CONES EarthSat Google • Small volcanoes composed entirely of cinders (from ash to bus size) • Their slope is between 30o and 33o • Typically composed of basalt (iron-rich volcanic rock) • Usually erupt only once within 10’s of years • May erupt lava flows • May exist on Mars? USGS – SP Crater, AZ

5. Cinder eruption in Mexico, 1943 to 1952 cinder cone lava flow Peter Kresan Town of Paricutín engulfed by lava flows – only church remains

6. Jim Todd Aerial Photography San Francisco volcanic field, Arizona one square mile USGS • Sunset crater one of 600+ cinder cones in the area • Sunset crater erupted between 1064 and 1065 A.D. • Hollywood wanted to blow it up during the 1920’s

7. Are there Cinder Cones on Mars? cinder cones impact craters one square mile THEMIS image Isidis Planitia (12N, 90E)

8. STRATOVOLCANOES tephra • Typically erupts tephra and lava • Composed of a “sticky” lava (high viscosity) • Makes steep slopes; usually capped by snow • Usually erupts for 10,000’s years • Common on Earth, not apparent Mars Java, Indonesia Mark Lewis (Photo Researchers)

9. canyons crater rim lava dome in crater blankets of ash USGS Space Imaging, IKONOS satellite view As seen from space Mt. St. Helens, 1980 tephra eruption (ash) Mt. St. Helens as seen from ground after eruption USGS

10. www.space.com Mt. Fuji from space Other Stratovolcanoes Mt. Fuji, a stratovolcano in Japan USGS

11. View of Hawaiian islands from space, USGS SHIELD VOLCANOES • Has a flattened cone shape • Hawaii has largest volcano on Earth: 56,000 feet high (10+ miles) • Can erupt for millions of years • Most common type of volcano on Mars

12. satellite view Shield Volcanoes caldera lava flows Satellite view, NASA • Mauna Loa’s is the active volcano on Hawaii • The basalt flows originate from the central vent at the summit, called a caldera • Eruption on flanks of Mauna Loa are typical (smoke trails above)

13. caldera summit lava flows ground view Mauna Loa, Hawaii. J.D. Griggs, USGS Typical shield volcano • Lava is very fluid (low viscosity) and flows over long distances • Lava is made of basalt • Lava tubes or tunnels are common

14. Shield volcanoes make lava tubes USGS • As lava flows down hill, it cools on all sides over time • Lava continues to flow inside the lava flow, insulated by the lava rock • This creates an underground river of lava called a lava tube or tunnel • Lava tubes can remain hollow after the lava has been drained • Over geologic time a lava tube or tubes can collapse

15. lava flow cinder cone lava tube Australian Undara lava tube Lava tubes on Earth Google Earth

16. Lava tubes on Mars lava tube impact crater one square mile THEMIS image

17. Fissure and Lava Flows on Mars fissure or crack lava flows • Fissure eruptions are often associated with shield volcanoes • Magma often travels up through these fissures and erupts onto the surface as lava one square mile 17N 240E THEMIS image

18. Review Cinder Volcanoes • Short-lived • Smallest • Tephra and flows Stratovolcanoes • Medium-lived • Medium-sized • Sticky lava • Tephra eruptions Shield Volcanoes • Long-lived • Largest • Fluid lava (basaltic) • Flows and lava tubes USGS, SP crater, Arizona USGS Satellite view, NASA