Volcanoes on Earth
USGS, SP crater, Arizona
How are volcanoes and their
features created?
How are volcanoes made?
and onto the surface
as Lava and/or tephra
through cracks or
faults in the crust
Magma rises up from
the mantle under
pressure
USGS
What are the major types of volcanoes?
Shield Volcanoes
Figures
from
USGS
Stratovolcanoes
(composite)
Cinder Cones
CINDER CONES
EarthSat Google
flow
crater
USGS – SP Crater, AZ
cone of cinders
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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?
Cinder eruption in Mexico, 1943 to 1952
cinder
cone
lava
flow
Peter Kresan
Town of Paricutín engulfed by lava flows – only church remains
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
Jim Todd Aerial Photography
Are there Cinder Cones on Mars?
one
square
mile
cinder cones
impact
craters
THEMIS
image
Isidis Planitia (12N, 90E)
STRATOVOLCANOES
tephra
Java,
Indonesia
Mark Lewis (Photo Researchers)
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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
Mt. St. Helens, 1980
tephra eruption (ash)
Mt. St. Helens as seen
from ground after
eruption
crater rim
blankets of ash
USGS
lava
dome in
crater
USGS
canyons
As seen from space
Space Imaging,
IKONOS satellite view
Other Stratovolcanoes
Mt. Fuji, a stratovolcano
in Japan
www.space.com
USGS
Mt. Fuji from space
SHIELD VOLCANOES
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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
View of Hawaiian islands from space, USGS
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)
Typical shield volcano
caldera summit
lava flows
ground view
Mauna Loa, Hawaii. J.D. Griggs, USGS
• Lava is very fluid (low viscosity) and flows over long distances
• Lava is made of basalt
• Lava tubes or tunnels are common
Shield volcanoes make lava tubes
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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
Lava tubes on Earth
lava flow
cinder
cone
lava tube
Australian Undara lava tube
Google Earth
Lava tubes on Mars
lava
tube
impact crater
one square mile
THEMIS
image
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
THEMIS
image
17N 240E
Review
Cinder Volcanoes
USGS, SP crater,
Arizona
– Short-lived
– Smallest
– Tephra and flows
Stratovolcanoes
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Medium-lived
Medium-sized
Sticky lava
Tephra eruptions
USGS
Shield Volcanoes
Satellite view,
NASA
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Long-lived
Largest
Fluid lava (basaltic)
Flows and lava tubes