Volcanoes Shield Volcanoes What Where Life Cycle with reference - - PowerPoint PPT Presentation

Volcanoes

Shield Volcanoes What Where Life Cycle with reference to Kauai Composite Volcanoes

Shield Volcanoes

What are they?

“A shield volcano is a type of volcano usually built almost entirely of fluid lava flows. They are named for their large size and low profile, resembling a warrior's shield.” (Wikipedia)

Shield Volcanoes

“effusive emissions of fluid lava”

thin sheets (1-3 m thick); gradual buildup; often near-continuous eruption

Shield Volcanoes

flat profile but can be very large mountains

• ften 3 – 4 miles diameter and half a mile high

largest: Mauna Loa

• over 60 miles wide,
• almost 14,000 ft above sea level

(and most of it is below sea level);

• 19,000 cubic miles of basalt

Shield Volcanoes

Height is typically 1/20 of width; steeper in the center

Shield Volcanoes

characteristic features:

• rift zones
• fissure venting
• lava tubes
• splatter cones
• calderas

Shield Volcanoes

characteristic features:

• rift zones

Shield Volcanoes

characteristic features:

• rift zones

Shield Volcanoes

characteristic features:

• lava tubes

Shield Volcanoes

characteristic features:

• splatter cones

Shield Volcanoes

characteristic features:

• fissure venting

Shield Volcanoes

characteristic features:

• Calderas - pits formed by the collapse of

land after a volcanic eruption

• NOT craters
• triggered by

emptying of magma chamber

Shield Volcanoes

characteristic features:

• Calderas

Shield Volcanoes

Where are they?

• Hotspots
• Rifts (divergent plate boundaries)
• Subduction zones

Shield Volcanoes

Where are they?

• Hawaii
• Galapagos Islands
• Iceland
• East Africa

Shield Volcanoes

Where are they? - the big 4

Shield Volcanoes

Hawaii

hotspot 80 million years 3 active volcanoes

• Mauna Loa
• Kilauea
• Lo`ihi

hundreds of islands and seamounts standard life-cycle

Shield Volcanoes

Galapagos Islands

Hotspot 4.2 million – 700,000 years old 13 considered active no clear age progression among islands

Shield Volcanoes

Iceland

mid-Atlantic ridge rift AND hotspot very young – 5,000 – 10,000 years Also has composite volcanoes

Shield Volcanoes

East Africa

rift zone, some hotspots On a continent young, several active long-lasting lava lakes (Erta Ale in Ethiopia since 1967, possibly 1906)

Shield Volcanoes

Others that are active:

• Mt. Okmok – Aleutians
• Mt. Edziza, British Colombia

Bottom half of Mount Erebus (Antarctica) Bottom half of Mount Etna (Sicily, Italy) Mount Karthala (Comoros) Niuafo'ou (Tonga) Mount Nyamuragira (Democratic Republic of the Congo) Piton de la Fournaise (Réunion, France) Masaya Volcano, Nicaragua

Shield Volcanoes

All active

Shield Volcanoes

Dormant:

Canada Heart Peaks Itcha Range[7] (British Columbia, Canada) Lava plateau of the Level Mountain Range[1] (British Columbia, Canada) United States Newberry Volcano in central Oregon Indian Heaven (Washington) Mauna Kea (Hawai'i) Hualālai (Hawai'i) Haleakalā (Maui) Medicine Lake Volcano (California) House Mountain Volcano (Arizona)

Shield Volcanoes

Dormant:

Kenya Mount Marsabit Menengai Other La Grille (Comoros) Queen Mary's Peak (South Atlantic Ocean) Rangitoto Island (New Zealand) Santorini (Greece) São Tomé (São Tomé and Príncipe, Atlantic Ocean) Skjaldbreiður (Iceland) Mount Takahe (Marie Byrd Land, Antarctica) Taveuni (Fiji) Karaca_Dağ (Turkey)

Shield Volcanoes

Extinct:

Antarctica: Mount Andrus, Mount Berlin, Mount Moulton, Mount Sidley (Marie Byrd Land), Mount Terror (Ross Dependency) Banks Peninsula (Christchurch, New Zealand) Bermuda Pedestal (Bermuda, United Kingdom) Dunedin Volcano (Dunedin, New Zealand) Kohala (Hawai'i, United States) Kookooligit Mountains (St. Lawrence Island, Alaska) Lord Howe Island, (Australia) Mount Warning, Australia Piton des Neiges (Réunion, France) Poike, Rano Kau, Terevaka (Easter Island, Chile) Verkhovoy (Kamchatka Peninsula, Russia.)

Shield Volcanoes

In short, not very many of them.

• maybe 40 or 50 active
• 20 to 30 dormant
• 15 – 20 extinct

Shield Volcanoes

In short, not very many of them. How many active volcanoes known?

Erupting now: perhaps 20 Each year: 50-70 Each decade: about 160 Historical eruptions: about 550 Known Holocene eruptions (last 10,000 years): about 1300 Note that these figures do not include the large number of eruptions (and undescribed volcanoes) on the deep sea floor.

Shield Volcanoes

However... There are shield volcanoes on Mars, Venus, and Io

Shield Volcanoes

Mars:

• enormous (up to 14 MILES high, 370 MILES

across: Olympus Mons)

• no longer active

Shield Volcanoes

Venus

• large (up to 430 miles across)
• quite flat
• many may still be active

Shield Volcanoes

Io – a moon of Jupiter

• most volcanically active body in solar system
• energy source

is tidal heating

• hundreds of

volcanic centers

• lava flows often

more than 300 miles

Shield Volcanoes

Io – a moon of Jupiter

• long-lasting lava lakes
• pyroclastic plumes (60 – 120

miles high, red/white/gray/black fans to 300 miles from the vent)

• mafic and ultramafic lava with sulfur

compounds that create colors

Homework

1) Make a list of the 8 most important points in today's presentation. 2) Go through your midterm exam and compare your answers to those I handed

• ut. For every answer you got wrong, write,
• n the exam, the page of the textbook

where the correct answer is found.