volcanoes 12 3 notes 08 09
DESCRIPTION
TRANSCRIPT
Igneous Rock Features
• Igneous- “from fire”, one of 3 major types of rock • Most magma cools & solidifies underground to form
hard, very dense rock
– Result in different sizes and shapes of rock bodies that are visible at the surface when the overlying rock is weathered and eroded away
– Called intrusive when they form below the surface
– Slow cooling causes rock to have large crystals
Most common are:
• Batholiths
• Dikes
• Sills
• Volcanic necks
also
• Calderas
Batholiths
Batholiths
Baja Batholith (southern CA)
Batholiths
The largest intrusive rock bodiesCan be many hundreds of kilometers wide
and long, and several kilometers thick
Yosemite National Park in CA
Yosemite National Park in CA
What is the difference between a dike and a sill?
Dikes
Ship Rock, NM
Morocco
Sills
Sills
Sills
Volcanic necks
Devil’s Tower, WY
Volcanic necks
• Magma inside vent hardens
• Softer rock of cone and surface weathers and erodes away
• Hard, dense igneous rock is exposed
Calderas
an unusually large crater or the remains when the cone collapses into its own magma chamber
Formation of Crater Lake