Transcript Sedimentary rocks

Sedimentary rocks
Sedimentary rocks
• Rocks that form from an accumulation of
sediments derived from preexisting rocks
and/or organic materials.
• These rocks form by various process that
occur on or within the top few kilometers of
earth’s crust
• Most sedimentary rocks are made up of solid
fragments or sediments, often called “clasts”,
that have been weathered or eroded from
older rocks.
• Clastic texture rocks are composed of smaller
rock fragments called sediments. Classified by
their particle size
Pebbles, cobbles and/or boulders
some silt sand or clay
Sand
Size of particles: from .0006cm to .2cm
Silt particles
Particle size: .00004 to .006
cm
Clay
Clay magnified 1,600 times
Particle size: less then .0004 cm
Cementation
• Often the clasts, such as sand, silt, and
pebbles, are cemented together in a process
called cementation. This happens as the
sediments lose water and the dissolved
minerals in the pores of the sediments
forming a crystalline mineral material
Chemical sedimentary rock
Crystalline Texture
• When dissolved minerals drop out of water
(precipitate), they form a mass of intergrown
or interconnected mineral crystals
• You can see crystals in the rock. The crystals
are composed of only one mineral
Bioclastic
• No crystals, No rock particles. May have shell
or shell fragments in it, or be completely black
in color consisting of dead organic material
Limestone
Coal