Volcanoes Lavas Minerals Allan Treiman LPI Heat Within

Volcanoes, Lavas, Minerals Allan Treiman LPI Heat Within, 2009

Plan of Talk v Breaking the Tyranny of Three – Three types of volcanoes – Three types of lavas v Volcanoes explained simply – Lava Properties – Eruption Style – Eruption Environments Lava Properties in terms of Atoms v Igneous Rocks and Minerals v

Three Types of Volcanoes ? Shield v Composite / Stratovolcano v Cinder Cone v

At real scale. v Like comparing a brick to a brick building

So Many More Kinds of Volcanoes Caldera Complex ‘Super. Volcano’ v Lava Plateau v Dome v Single Flow v Tuff Ring v And … v

What Controls the Shape of a Volcano? v Properties of lava – Viscosity (runny or stiff) – Dissolved Gas - Explosive or Effusive – % Solid grains in lava Volume and Rate of each eruption v Number of individual eruptions v Environment around eruption v

What is Lava? What is lava? – Molten material at a planet’s surface – Solidifies at surface conditions v Many sorts of ‘lava’ – Most common is silicate - abundant Si. O 44– Molten sulfur, carbonate, iron oxide – Mud is not lava, really (but “mud volcanos”) – Water is not lava on Earth (but is elsewhere) v What is magma? – More general - not necessarily erupts

Silicate lavas molecular! v v v Si - O bonds much stronger than others Silica tetrahedra, Si. O 44 -, polymerize In lava, single silica tetrahedra flow past each other easily, like cous-cous v v In lava, large silicate polymers tangle together, like spaghetti, and flow poorly

More Silica (Si. O 2) = bigger, more connected polymers v Low Silica (Si. O 2 < 52%) is basalt – Runny as motor oil, or corn syrup v Intermediate Silica – Andesite: 52 - 63% Si. O 2 – Dacite: 63 - 68 % Si. O 2 – Stiffer than taffy v High Silica, > 68 % Si. O 2 gives 3 -D polymers – Rhyolite/Granite - flows like window glass

Why does Vapor Matter? v Force for explosive eruptions – Water & CO 2 vapor bubbles out as magma nears surface – No vapor, no explosion! Stiff water-rich magma makes foam (pumice) & shards of glassy ash - huge eruptions v Pumice + ash and water vapor can flow together as a ‘slurry’ = an ash flow v

Volcanic Ash!

Ash flow = pyroclastic flow Video at http: //www. geo. mtu. edu/volcanoes/west. indies/soufriere/govt/images/051296/

Caldera Complex “Super-Volcanos” Yellowstone v v Valles Grandes, NM Caldera is 22 km across Rhyolite ash flows & domes Slope outside caldera ~2°

Crystals in Lava Solid crystals make lava more viscous v What kinds of crystals? v – Olivine (Mg, Fe)2 Si. O 4 - olive green, glassy – Pyroxene (Ca, Mg, Fe)Si. O 3 - black/green, breaks on flat surfaces (cleavage) – Feldspar - plagioclase (Ca, Na)(Al, Si)Si 2 O 8 clear-white-greenish, glassy, breaks on flat surfaces. – Quartz - Si. O 2 - clear, glassy, curved fractures. v Stop to look at minerals & rocks …

Single Eruption or Flow v v Paricutin Cinder Cone - 1. 4 km 3 lava (typical) Columbia River, Grande Ronde - to 750 km long, 2000 km 3 lava Yellowstone - Lava Creek Tuff (like at Valles Caldera) ~1000 km 3 ash How much is a cubic kilometer?

Many Eruptions Mauna Loa Shield ~75, 000 km 3 lava v Columbia River Basalts ~170, 000 km 3 lava v Olympus Mons (Mars) ~500, 000 km 3 lava v Ontong-Java Plateau ? 6, 000 km 3 lava v

Environment of Eruption v Into Air – Typical v Into Water – Maar Crater – Tuff Ring – Pillow Lava v Into Ice – Tuya Buttes v Into Vacuum ?

The End.