Download Rocks - Hewlett

Rocks
Rock Origin
• Igneous Rocks - Formed from the
cooling of molten magma or lava.
• Sedimentary Rocks- Formed from
particles of other rocks or remains of
plants and animals that are cemented
together in layers.
• Metamorphic- Formed when an existing
rock is changed by extreme heat and
pressure, usually takes place deep under
ground.
• Aim: How do igneous rocks
form?
Igneous rocks
• All have crystals.
• All result from magma or lava
• Origin
– Extrusive Igneous rock
• Formed from lava eruption, which means it formed on
earth’s surface.
– Intrusive Igneous rock
• Igneous rock formed when magma hardened beneath
earths surface.
Igneous rock cont.
• Texture
– Depends on mineral crystals.
• Rapid cool = fine grained (Small Crystals)
• Slow cool = coarse grained (Large Crystals)
• Porphyritic = cools slow then fast (both small and large
crystals)
• Intrusive rocks have larger crystals than extrusive.
• Mineral composition
– See reference table pg 6
• Uses of igneous rock
– Building = Cobblestone, Curbs, stone Statues, Huge
Ancient Structures.
Igneous rock formation
Sedimentary Rocks
• Sediments that come from rock and living things are
deposited in layers and become sedimentary rock.
Formation
• Erosion = Water and Wind loosening and carrying away
fragments of rock.
• Deposition = settling of sediments.
– Pieces of shells, bones, leaves and so forth can also be
deposited.
• Compaction = pushing sediments together.
• Cementation = minerals crystallize in the spaces
between sediments and cement the sediments together.
Sedimentary Rock Formation
Types of Sedimentary Rocks
• Classified by the types of sediments
• Clastic rocks
– Formed from broken pieces of other rocks.
– Examples
• Shale = clay particles
• Sandstone = sand
• Conglomerate = large pebbles
• Organic rocks (bioclastic)
– Formed from the remains of substance that were once
living
– Examples
• Coal = Remains of swamp plants buried in water
• Limestone = Hard shells glued together.
Types of Sedimentary Rocks
• Chemical Rocks
– Formed when mineral dissolved in solution and
crystallize.
– Examples
• Gypsum = from evaporation
• Limestone = From dissolved calcite ( different than organic)
Use of sedimentary rocks
• Used in building supplies because of ease to cut
and shape ( White House is sandstone).
Metamorphic
• Heat and Pressure deep beneath the earth’s
surface can change any rock to metamorphic
rock.
• The change results in a different appearance
texture, crystal structure, and mineral content.
Classifying
• Done by looking at grain arrangement.
– Arranged in bands = foliated ex. slate
– Random arrangement = Nonfoliated rock ex. marble
Metamorphic Rock Formation
The Rock Cycle
• is a group of changes. Igneous rock can change
into sedimentary rock or into metamorphic rock.
Sedimentary rock can change into metamorphic
rock or into igneous rock. Metamorphic rock can
change into igneous or sedimentary rock.
Igneous rock forms when magma cools and
makes crystals. Magma is a hot liquid made of
melted minerals. The minerals can form crystals
when they cool. Igneous rock can form
underground, where the magma cools slowly.
Or, igneous rock can form above ground, where
the magma cools quickly.
Interactive
Rock Cycle
Animation