Rock Cycle
Rock Cycle –
* interrelationships between rock types
* Metamorphic rock melts → magma
* Magma crystallizes → igneous rock
* any rock erodes → sediment
* sediment lithifies (cements together) →
sedimentary rock
* any rock undergoes heat and/or pressure
→ metamorphic rock
Igneous Rocks
- Form as magma cools & crystallizes
* if it cools below surface = plutonic or intrusive
* if it cools on surface from lava = volcanic or
extrusive
- Crystallization Patterns
(orderly pattern of atoms)
* slow rate = large crystals
* fast rate = small crystals
* very fast = glass texture (no crystals)
Igneous Classification –
- depends on texture & composition
* Texture (size & arrangement of crystals)
* fine-grained (cooled quickly)
* coarse-grained (cooled slowly)
* porphyritic– 2 crystal sizes caused by 2
rates of cooling
Extrusive (Volcanic) Igneous Rocks
Obsidian – glassy
texture (note
conchoidal fracture),
few gases in lava
Pumice - “frothy”
texture, holes indicate
high amount of gases
escaped at lava extruded
to surface
Intrusive (Plutonic) Igneous Rocks
Rhyolite – fine
grained, coled quickly
nearer surface
Granite – coarse-grained,
cooled more slowly and
deeper below surface
Porphyry- 2 different
crystal sizes, big crystals
formed slowly, smaller
(matrix) crystals formed
quickly