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Chapter 5

ESS102H1 Chapter Notes - Chapter 5: Silicate Minerals, Igneous Rock, Lithification

Earth Sciences
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[GLG Text Notes Chapter 5] 1
Chapter 5: Rocks and Rock-Forming Processes
Sandstone: a rock composed of rock grains
Important knowledge of rock-forming processes (at beach) :
oFor some rocks, the mineral constituents are pieces of other rocks with
the addition of some biologically produced mineral matter
oAn abrasion process—the grinding together of pieces together during a
transport by moving water or wind—reshapes the fragments
oFragments of older rock consolidate into new rock by the addition of
mineral cement
Important knowledge of rock-forming processes (at a spring) :
oSome rocks form by precipitation of minerals from water that cements
loose sediment together, or by intergrowth of precipitated minerals
Important knowledge of rock-forming processes (at a volcano) :
oA major difference is the shape of the mineral grains in the sandstone
compared to those in the volcanic rock; the mineral grains in the
volcanic rock have sharp edges and flat surfaces representing the
crystal faces whereas those in the sandstone are rounded and do not
preserve crystal outlines; minerals in the volcanic rock crystallized in the
place from the original molten material and were not tumbled and
abraded during transport by moving wind and water
oIntergrowth of newly formed minerals explains the solid nature of the
rock formed at both the spring and the volcano; these rock types
different, however, in that the rock at the spring formed by precipitation
of minerals out of water that remained liquid; the volcanic rock formed
by the complete crystallization of a molten-rock liquid
Most natural rocks are aggregates of mineral grains
Many rocks originate from observable processes that take place at Earth’s
The presence of rocks that are not related to observable surface processes
suggests that they relate to processes active within the Earth
Descriptive classifications group items of similar appearance for their origins;
genetic classifications group features or phenomena by noting similarities in
the processes that cause or create them
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