• Increasing Temperature
• Decreasing Pressure
• Addition of Water

Environments of Magma Formation
• Spreading Center
• Mantle Plume
• Subduction Zone

Mantle Plume: Hot Spots
Hawaii Island animation
Iris Hot Spot

Subduction Zone

• Asthenosphere is “PERIDOTITE”
• PERIDOTITE =“OLIVINE+PYROXENE+ Ca-Feldspar”
Olivine  1,890°C, Pyroxene  1,390°C,
Calcium Feldspar  1,550°C
Peridotite  1,270°C the product of the first melt Rich In Silica
Partial Melting: A small amount of original peridotite melts to form basaltic magma

• When a large granitic magma solidifies with in
Earth’s crust to form a large mass of Granite called a pluton

• Pahoehoe  Low Viscosity, as it cools stiffens forming smooth, glassy surfaced, wrinkled or ropy ridges
• Aa  higher viscosity surface partially solidify as it flows
• Pillow lavas  is a lava structure that typically when lava is emerged from an underwater volcanic vent.
• Pyroclastic rock  rock fragments
• Volcanic Ash

• When lava is too viscous to spread out as a flood it builds a hill or mountain call Volcano

• Basaltic Magma
• Gentle sloping mountain
• at angles 6° to 12°

• Small volcano composed of Pyroclastic fragments
• Large amount of gas accumulates in rising magma

• Stratovolcano
• form by longs periods of time by alternating lava flows and pyroclastic material

Volcanic Eruptions and
Global Climate