earth science - volcanoes

The Fiery Earth

• There are 4 types of volcanism

on Earth

1. Shield cones

2. Cinder cones

3. Composite cones

4. Fissure Eruptions

Volcanoes

• Large volcanoes with broad bases and gently sloping sides

– Lava composition is mafic – Few gases– Relatively quiet eruptions– Igneous rocks created: Basalt; some Scoria

SHIELD CONES

Mauna Loa, Hawaii

Mauna Kea, Hawaii

• Small volcanoes with steep slopes

CINDER CONES

– Lava composition is felsic, however generally low silica

– Higher gas content

– Explosive eruptions

– Igneous rocks created: Scoria

Lava Butte, Oregon

Cerro Negro, Nicaragua

• Tall, steep volcanoes made of alternating layers of hardened lava flows.

– Lava composition is felsic

– Gases vary– Both quiet and

explosive eruptions– Igneous rocks created:

Pumice, Obsidian, Rhyolite

COMPOSITE CONE

Mount St. Helens, Washington

Mount Pinatubo, Phillipines

• Fracture or crack from which lava erupts

– Lava composition is mafic – Few gases– Quiet eruptions, repeated layers– Igneous rocks created: Basalt

FISSURE

ERUPTIONS

• Tiny jagged pieces of rock and glass

– After an eruption, wind can carry ash far away

– Most settles on the land around the volcano

Volcanic Ash

• Aa – jagged chunks of lava formed by rapid cooling.

LAVA FLOWS

• Pahoehoe – forms a wrinkled, ropy texture as the lava cools.

LAVA FLOWS

• A fast moving flow of mud, rocks, and debris

LAHAR

– occurs when water from glaciers is released due to a volcanic eruption

• A fast-moving, dense, super-heated, poisonous gas cloud.

PYROCLASTIC FLOW

• Large clots of lava thrown out of an erupting volcano

VOLCANIC BOMBS

– while red-hot, spin through the air, cool, and develop a round or spindle shape.

Images

1. Ellen van den Berg, “The Skjaldbreiour Shield Volcano” September 2, 2009 via Flickr, Attribution-NonCommercial-NoDerivs License http://farm3.staticflickr.com/2422/3903567972_aab3c8429a_z.jpg

2. Dan Dzurisin, “Overlook Vent and Mauna Loa, Predawn” June 15, 2008 via Flickr, Attribution-NonCommercial-NoDerivs License http://farm4.staticflickr.com/3024/2582939400_e0aeeb30a2_z.jpg

3. Hector Parayuelos, “Maua Kea 1” September 5, 2009 via Flickr, Attribution-NonCommercial-NoDerivs License http://farm8.staticflickr.com/7168/6620817281_b2a6079619_z.jpg

4. Tim Rawle, “Cinder Cones of Hale Pohaku” March 25, 2009 via Flickr, Attribution-NonCommercial-NoDerivs License http://farm3.staticflickr.com/2436/3543949826_5540b79619_z.jpg

5. Rhiannon Boyle, “Lava Butte” August 2, 2010 via Flickr, Attribution-NonCommercial-NoDerivs License http://farm5.staticflickr.com/4080/4880719919_7aaa7082dd_z.jpg

6. Garrett Ziegler, “Cerro Negro, Nicaragua” May 29, 2012 via Flickr, Attribution-NonCommercial-NoDerivs License http://farm9.staticflickr.com/8025/7355197970_accf1e28df_z.jpg

7. Jessica, “Mount Fuji” November 16, 2012 via Flickr, Attribution-NonCommercial-NoDerivs License http://farm9.staticflickr.com/8204/8230795750_7e493a8f3a_z.jpg

8. Dave Schumaker, “Mount St. Helens” August 19, 2009 via Flickr, Attribution-NonCommercial-NoDerivs License http://farm4.staticflickr.com/3518/3844015809_40d284ab40_z.jpg

Images, continued

9. Storm Crypt, “Pinatubo’s Northeast Shore” August 16, 2008 via Flickr, Attribution-NonCommercial-NoDerivs License http://farm4.staticflickr.com/3128/2927114406_0e573f4175_z.jpg?zz=1

10. Islomaniac, “New lava fountain eruption from smoldering fissure” March 2011 via Flickr, Attribution License http://farm6.staticflickr.com/5175/5536447923_01e3470e13_o.jpg

11. Finnur Malmquist, “Eruption in Eyjafjallajokull” May 7, 2010 via Flickr, Attribution-NonCommercial-NoDerivs License http://farm5.staticflickr.com/4070/4588825332_58d859df97_z.jpg

12. ccarlstead, “Aa Lava Flow” January 13, 2011 via Flickr, Attribution-NonCommercial-NoDerivs License http://farm6.staticflickr.com/5171/5412138468_0c097402b8_z.jpg

13. Zack Jackson, “Lava” January 12, 2005 via Flickr, Attribution-NonCommercial-NoDerivs License http://farm4.staticflickr.com/3078/3241111818_78c08cc901_z.jpg

14. UWI Seismic Research Centre, “Lahar flow in Plymouth” May 20, 2005 via Flickr, Attribution-NonCommercial-NoDerivs License http://farm3.staticflickr.com/2443/3706671983_801e8f2989_z.jpg

15. gnuckx, “Italy Etna Volcano” October 27, 2008, Attribution License http://farm4.staticflickr.com/3484/3208523096_6ba9e9c115_z.jpg

16. GabeD, “Galapagos-Isabela” December 28, 2008 via Flickr, Attribution-NonCommercial-NoDerivs License http://farm4.staticflickr.com/3261/3203163476_5d233f099b_z.jpg?zz=1