Lesson 5 Volcanoes: The Basics

Nyiragongo Volcano East African Rift Valley What is magma? A mixture of molten rock, suspended mineral grains, and dissolved gases deep beneath Earth’s surface http://www.pbs.org/wgbh/nova/volcanocity/anat-08.html Nyiragongo Volcano East African Rift Valley

2. Types of Magma: Basaltic… http://www.ncgeology.com/Eno_interactive_webs/Geologic_Principles_igneous%20rocks.html 2. Types of Magma: Basaltic… Gas Content 1 – 2 % Silica Content 50% Viscosity low Explosiveness least Origin/Location of Magma/Lava oceanic/continental crust Example Mt. Kilauea in Hawaii Mt. Kilauea A Hot Spot Volcano

Types of Magma: Andesitic… Gas Content 3 - 4 % Silica Content 60% Viscosity intermediate Explosiveness Origin/Location of Magma/Lava continental margins Examples… Mt. St. Helens and Mt. Rainier (Washington) http://vulcan.wr.usgs.gov/Volcanoes/MSH/Images/july_22_images.html

Types of Magma: Rhyolitic (Granitic) Gas Content 4 - 6 % Silica Content 70% Viscosity high Explosiveness greatest Origin or Location of Magma/Lava continental crust Example Yellowstone Supervolcano in Wyoming Yellowstone Volcano

Types of Magma… 3. The higher the silica content… http://www.hbci.com/~wenonah/history/img/krakatoa.jpg Types of Magma… 3. The higher the silica content… the higher the viscosity (resistance to flowing)… the greater the explosiveness! Krakatoa – Highly viscous and explosive!

Intrusive Activity… What is a pluton? An intrusive igneous rock body http://romanmythology.wikia.com/wiki/Pluto Intrusive Activity… What is a pluton? An intrusive igneous rock body Pluto – god of the underworld http://earthsci.org/mineral/rockmin/chart/iroccur.gif

http://www.yosemiteriversideinn.com/ Batholiths 2. A batholith is the largest of plutons common in the interiors of major mountain chains. Yosemite – Part of the Sierra Nevada Batholith

Intrusive Activity… At subduction zones, a plate subducts, melts, Where did all the magma come from? Scientists hypothesize that… At subduction zones, a plate subducts, melts, cools into a pluton. http://herramientaslinker.com.ar/convergent-boundary-subduction&page=7

Volcanoes… What is lava? What is a volcano? http://www.smate.wwu.edu/teched/geology/vo-eruption2.html Volcanoes… What is lava? molten rock that has reached Earth’s surface What is a volcano? A mountain or opening in Earth’s crust from which lava erupts Paricutin in Mexico, 1943

3. The Anatomy of a Volcano… Vent – the opening in the crust through which lava erupts Crater – bowl-shaped depression around the vent Caldera – larger depressions around a vent where the volcano has collapsed into the magma chamber d. Magma chamber – area under the volcano which holds the magma

4. Label the Volcano… http://rbaadvisors.com/what-are-the-main-features-of-a-volcano&page=3

Types of Volcanoes… Shield Basaltic lava builds up (Quiet eruptions) http://www.cnn.com/2014/10/28/us/hawaii-volcano/index.html IN THE NEWS… Type of Volcano Shield How It Forms Basaltic lava builds up (Quiet eruptions) Description Wide with gently-sloping sides Example Kilauea in Hawaii (hot spot) Iceland (divergent) http://www.discoverhawaiitours.com/blog/tag/kilauea/

Types of Volcanoes… Type of Volcano How It Forms Description Example Cinder cone How It Forms Ejected tephra falls back to earth and piles up (Explosive) Description Small but steep Example Paricutin in Mexico Convergent boundary Paricutin, Mexico http://volcano.oregonstate.edu/vwdocs/volc_images/img_paricutin.html

Types of Volcanoes… Type of Volcano Composite How It Forms Tephra eruptions alternate with lava flows Description Large & steep Example Krakatoa Mt. St. Helens Convergent Mt. St. Helens -Before and After! http://pubs.usgs.gov/fs/2005/3045/images/fig1.jpg

A Composite Volcano… http://www.pbs.org/wgbh/nova/volcanocity/anat-flash.html

Volcanoes: Effects on the Lithosphere Lesson 6 Volcanoes: Effects on the Lithosphere

Tephra… 1. What is tephra? Tephra classified by size… Rock fragments thrown into the air during a volcanic eruption Tephra classified by size… dust  ash  lapilli  bombs  blocks 2. A pyroclastic flow is… an eruption of gas, ash, and other tephra These types of eruptions can be extremely violent and deadly because… the PC flow moves very fast and is very hot. 3. Ash and dust from a pyroclastic flow blocks sunlight and lowers global temperatures.

Effects of a Volcanic Eruption… Lahars A lahar is a mixture of mud & debris created when… heat from an eruption melts snow OR rain forms around dust or ash in the atmosphere. http://volcanoes.usgs.gov/hazards/lahar/index.php

Earthquakes, Landslides and Tsunamis… Earthquakes are caused when… Magma breaks rocks as it makes its way to the surface. Landslides are caused in two ways… … a volcanic earthquake (EQ) or the eruption itself causes land to slide Tsunamis are caused when… … the volcanic landslide “bulldozes” water ahead of it

Earthquakes, Landslides and Tsunamis…

6. Kilauea: Effects on Land… Basaltic lava… burns vegetation and buildings creates new land (16 acres a year!) http://www.ncgeology.com/Eno_interactive_webs/Geologic_Principles_igneous%20rocks.html

7. Krakatoa: Effects on Land… The eruption of Krakatoa… Created a caldera when it blew the island apart Caused a pyroclastic flow and tsunami (1883) http://www.ncgeology.com/Eno_interactive_webs/Geologic_Principles_igneous%20rocks.html

8. Iceland: Effects on Land… Iceland’s volcanoes in the rift valley are causing it to grow bigger – with older rocks on the east and west sides of the island.

Convergent Boundary Volcanoes Ocean plates subduct under other plates and melt to form magma Location – the Pacific Ring of Fire, the Mediterranean Belt Mt. Vesuvius and Pompeii Victims http://mrbpielglobal.edublogs.org/files/2010/12/vesuvius_24417-1qnp5rt.jpg

The Ring of Fire… http://pubs.usgs.gov/gip/dynamic/graphics/Fig22.gif

Divergent Boundary Volcanoes As plates move apart, magma is forced upward into fractures and faults Location – East Africa Rift Valley, mid-ocean ridges, Iceland

A Plethora of Plutons… Stocks Stocks are irregularly-shaped plutons similar to batholiths but smaller. http://belmont.sd62.bc.ca/teacher/geology12/photos/volcanoes/plutons.jpg

A Plethora of Plutons… Laccoliths http://facweb.bhc.edu/academics/science/harwoodr/geol101/study/Plutons.htm Laccoliths are mushroom-shaped plutons with a round top and a flat bottom.

A Plethora of Plutons… Sills http://facstaff.gpc.edu/~pgore/geology/geo101/plutons.php A Plethora of Plutons… Sills A sill is a pluton that forms when magma intrudes parallel to layers of rock. The Palisades Sill, NY