Download rocks - Mrs. DiLorenzo Earth Science

Sedimentary Rocks
What is a Rock?
• A rock is any naturally formed solid on Earth or in
any part of the universe.
• Rocks are grouped into three categories:
1. Sedimentary
2. Igneous
3. Metamorphic
• Rocks are described by their composition and
texture.
Sedimentary Rocks
• Sedimentary rocks are made from pieces of other
rocks and/or organic materials.
• Most sedimentary rocks form under large bodies
of water.
– Horizontal layers
• Once deposited, methods of formation include
cementation, compaction, chemical action, and
organic processes.
How do Sedimentary Rocks form?
1. Cementation: occurs when clasts are cemented
together.
– Calcite, quartz, & hematite are common cements.
– Clastic Sedimentary Rocks:
mainly composed of solid
sediments
2. Compaction: occurs when sediments are
squeezed together.
3. Chemical Action: occurs when minerals dissolved
in water precipitate out from the water, and form
a crystalline mass of intergrown crystals.
– “evaporites”
Salt Mine in Geneseo, NY
Limestone
towers at
Mono Lake,
California
4. Organic Processes: any rock made by living
organisms or mostly composed of materials from
life forms is an organic rock.
– “Bioclastic Sedimentary Rock”
Characteristics of Sedimentary Rocks
• Composed of fragments (sand, pebbles, etc.)
• Contain fossils
• Often layered
The Grand Canyon is made of layers of sedimentary rocks that are
200 million to nearly 2 billion years old, many containing fossils.
Identifying Sedimentary Rocks
• Clastic rocks are identified based on particle size.
Identifying Sedimentary Rocks
• Non-clastic rocks are usually made of one mineral,
so they can be identified like minerals.
Limestone is made of
the mineral calcite
Rock Salt is made of the
mineral halite
Rock Gypsum is
made of the
mineral gypsum