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Sedimentary & Metamorphic

Objectives:

    1.    Distinguish between the three types of sedimentary rocks.

    2.    Discuss different features of sedimentary rocks.

    3.    Explain the processes involved in the formation of sedimentary rocks.

    4.    Differentiate between the different forms of metamorphic rocks.

Key Terms:

    cementation    stratification        fossil    parent rock        metamorphism        deform

Notes: (6-3 & 6-4)

Sedimentary Rocks

Sedimentary rocks are perhaps the most common rocks found on Earth's surface.  They are made from the weathering and cementation of inorganic and organic sediments.  The formation can be further broken down into three classes.

Clastic Rocks:

Formed from fragments of other rocks
The rocks in this category are classified according to size of the pebbles
Types: Conglomerate, sandstone, shale

Shell conglomerate

           

Chemical Rock:

Made from dissolved minerals via precipitation
Types: Rock salt, limestone, gypsum

Organic Rock:

Formed from the sediments of organic remains of plants and animals
Fossil remains are organic rock
coal is another example

 

Metamorphic Rocks:

Metamorphism is the process by which a rock's structure is changed by heat and pressure.  The original rock is considered the parent rock and the rock it becomes is the metamorphic rock.  There are two distinct types of metamorphism.

  1. Regional metamorphism
    Occurs when large areas of rock change under extreme heat and pressure.
    Occurs during plate movements that cause mountain building
    minerals and rocks align themselves in layers
  2. Local metamorphism
    Contact - when rock comes in contact with cooling magma
    causes few changes in the rock
    Deformation - low heat and high pressure
    associated with faults

Causes of metamorphic rock

Changes are due to extreme changes in pressure, temperature, or composition

o     Temp. and press. is high enough to bond the minerals but not enough to melt them

Parent rock can be igneous, sedimentary of metamorphic in origin

Granite becomes gneiss

[Click for larger image]

Shale becomes slate

Sandstone becomes quartzite

limestone becomes marble

Classification

       Foliated Rocks

o     Grains are flattened into parallel bands

o     Gneiss & slate

       Nonfoliated Rocks

o     No banding

o     Sandstone becomes quartzite

o     Limestone becomes marble

Marble

 

 

 

Last modified: October 03, 2003