National Parks formed by Volcanic Activity part 1

1
National Parks formed by Volcanic Activity (part
1)

• Mount St. Helens National Volcanic Monument
• Crater Lake National Park

2
Volcanism

• Extrusive igneous rocks
• Different chemistry
• High Silica 70 Rhyolite
• Moderate Silica 60 Andesite
• Low Silica 50 Basalt
• Chemistry controls viscosity
• Rhyolitic very viscous
• Basaltic very runny

3
Volcanic Rocks

• Lava Flows
• Aa
• Pahoehoe
• Pyroclastic material (based on size)
• Ash Tuff
• Lapilli
• Blocks
• Pumice and Scoria

4
Types of Volcanoes

• Shield Volcano
• Composite cone
• Volcanic dome
• Cinder cone

5
Location of Volcanoes

• Divergent plate boundaries
• Mid ocean ridges
• Continental rift zone
• Convergent plate boundaries
• Oceanic-Oceanic Crust
• Oceanic-Continental Crust
• Hot spots

6
Mount St. HelensVital Statistics

• Southwest Washington
• 110,000 acres
• 170 square miles

7
History

• 6,500-3,500 years ago evidence of NA
• 3,500 years ago eruption
• 1,500 years ago - Numerous tribes
• 1792 British Royal Navy
• 1800 eruption
• Early 1800 Brit US exploration

8
History

• 1805-06 Lewis Clark
• 1831-1851 numerous small eruptions
• 1851-1980 inactive
• 1890-1910 mining
• 1982 Established by President Reagan as Mount
  St. Helens National Volcanic Monument
• Managed by the US Forest Service

9
Geologic Features

• The Volcano Mass Movements
• Stratovolcanic cone
• 18 MAY 1980
• Earthquake
• Debris avalanche from collapse of dome

10
Geologic Features

• The Volcano Mass Movements
• Lateral blast
• Ash Eruption Fallout
• Pyroclastic Flow
• New Crater
• Mud Flows

11
Geologic History

• Eocene 60-40 mya flat coastal lowland,
• sandstone, shale, coal
• 40 mya coastal plain sinks, volcanic islands form
• Volcanic rocks and sedimentary rocks
• 30 mya uplift
• 25 mya fissure basalts
• 10 mya erosion to low hills
• 1 mya Mt Rainier and other vol mts begin to form,
  glaciation

12
Activity since 1980

• 1980-1986 Continued activity,
• lava domes small eruptions
• Winters of 1989 1990 ash eruptions
• 1990-2004 relatively quiet
• 2004 new lava dome
• March 2005 minor eruption
• 2005-2008 minor ejections of steam

13
Crater Lake National Park
14
Vital Statistics

• Southwest Oregon
• 160,000 acres
• 290 square miles

15
Human History

• Klamath tribe
• Mid 1800s prospectors soldiers
• 1883 Scientific Studies
• 1885 drive to NP status begins
• 1902 NP signed by TR

16
Geologic Features

• Caldera of Stratovolcano
• Remnants of Mt. Mazama
• Igneous Dikes
• Cinder cones
• Glaciation

17
Geologic History

• Early history similar to other Cascades Volcanoes
• Mt. Mazama built starting 1 to 2 mya
• Glaciation during this construction
• 7000 years ago eruption
• Between 6000 and 1000 ya creation of cinder cones