Unit 12 Final

• Impacts of of meteorite.
• Compression caused by gravity of thousands of miles of overlying rock layers. 
• Heat generated by radioactive decay of elements in Earth's mantle and core.

Our moon is the product of collision between a Mars-sized planet and early Earth

Magma is molten rock below the Earth's surface. Lava is molten rock above the Earth's surface.

• Extrusive igneous rocks form from magma that solidifies after reaching the surface of the Earth. Gas bubbles are commonly found within this type of rock. 
• Intrusive rocks form from magma that solidified below the Earth's surface. Slow cooling produces large mineral crystals while quicker cooling forms smaller crystals.

Magma is less dense (lighter) than its solid rock phase because its molecules are further apart. This lower density will cause the magma to rise toward the surface (like the salt domes).

It represents the increase in temperature with depth into the Earth.

Increase of pressure with depth into the Earth.

From volcanoes.

Diamonds are brought to the Earth's surface by "kimberlite pipes" (a special type of explosive volcano).

Only 10%-20% of minerals melting are needed to produce a fluid magma.

• For convergent (subduction zones):
• Decreasing the pressure on hot solid rock BY FRACTURES (pressure relief melting) will lower the normal melting point of a mineral which can result in a magma. (Used a pressure cooker as an example.)
• Adding water to hot solid rock can lowr the normal melting point of a rock which can result in a magma.
• Divergent or rift zone:
• The hot crust will rise and fracture.
• The fracturing decreases the pressure on the hot rock which in turn will lower the normal melting point of a mineral which finally produces a magma (pressure relief melting).

Water vapor (a green house gas).

...

Carbon dioxide (a greenhouse gas).

Carbon dioxide  can also be deadly when first accumulated at the bottom of volcanic lakes-then expelled.

Acid can "alter" black scoria rocks into red scoria rocks.

• Tectonic divergent plate boundaries (mid-oceanic ridges and continental rifts).
• Tectonic convergent plate boundaries.
• Mantle plumes or hotpsots that rise from Earth's liquid iron core.

• Quartz and oroclase.
• Sand and ooze.

Felsic or silicic magma.

Mafic magmas.

• Felsic: assocaiated with intense, explosive volcanic activity. 
• Mafic: volcanic activity is relatively quiet compared to felsic volcanoes

• Felsic. The greater the content, the greater the viscosity of a lava, the slower the lava will flow. 
• Mafic: Formed in very liquid-like lavas which can flow almost like water (very low viscosity).

Solid material (igneous rock) blown from a volcano during and explosive eruption.

Volcanic dust represented by tiny, sharp-edged dust particles violently ejected from volcanoes (dangerous to inhale in large quantities).

West Texas.

Volcanic rocks that are larger than gravel size and are tapered from passage through air (while still molten).

Volcanic fibers that are long, glassy fibers of igneous rock produced from volcanic explosions. Pele's tears are small tear-shaped particles associated with volcanic fibers.

• Pahoehoe: rock formed by "fast-flowing" lava (typically has a ropy crust. 
• Aa: jagged, sharp-edged rock formed by relatively slow-moving, very viscous lava.

Pillow lava (pillow basalts).

550 active volcanoes.

Basalt lavas can flow like water down the volcano slope, making it almost impossible to build up a steep cone; shaped like a very broad dome.

In a belt that extends from Uvalde TX to Austin TX.

Almost destroyed the human race. It ejected more than 670 cubic miles of volcanic ash around the world. The resultant caldera is 65 miles long and 25 miles wide.

• Eruption in 1996 Montesseart.
• Mt. Pinatubo of the Philippines.
• Mt. Vesuvius in Pompeii, Italy.
• Mt. St. Helens in Washington State.

Today we find human molds of victims that were caught up and enveloped by the flow.

• By a volcano eruption.
• By magma exiting the side of the volcano.

Composite volcano.

Yellowstone have had three massive eruption, each about 200,000 years apart. The last one occurred more than 200,000 years ago. Yellowstone sits over a large pool of deep magma that is causing the area to rise and fall. Some are predicting another super volcano explosion.

• Mafic, continous massive flows of basalt from fautl zone. 
• Mafic magma can be extruded from very long cracks or fissures to "flood vast areas with basalt" thus the term flood basalts.

An eroded volcanic cone with the remaining intrusive exposed.

• Columns of rock created by polygonal cracks (contraction by cooling) found in mafic volcanic necks and in many mafic flows (sometimes can be found with silicic flows).
• 

Enchanted Rock, west of Austin, near Fredricksburg.

Olympus Mons on Mars, at more than 66,000 feet high.

Io.

• Grew from a crack in a cornfield to a large killer volcano in Mexico in 1943. 
• In 1949, a pyroclastic cloud from that volcano killed more than 1,000 locals attending a fiesta.

Result of a gas well blowout that caught fire in 1939.