laboratory 4 Flashcards
(33 cards)
Where do sedimentary rocks form?
On or near earth’s surface
What is erosion?
geological process in which materials are worn
away and (potentially) transported naturally by wind or
water.
What is weathering?
breaking down or dissolving of ROCKS
and MINERALS on Earth’s surface.
What are found on the Mt-Royal?
LIMESTONE (above) and SHALE
(below) found on Mount Royal are both
examples of SEDIMENTARY ROCKS
Weathering is driven by which factors?
WEATHERING driven by factors such as water, ice/snow, acids, salts, plants, animals and temperature fluctuations.
What do erosion and weathering have in common?
EROSION and WEATHERING slowly break down mountains, boulders, and larger rocks into smaller rocks and SEDIMENT/UNCONSOLIDATED MATERIALS
(gravel, sand, silt, clay)
What is dissolution?
(CHEMICAL WEATHERING): a form of
WEATHERING wherein slightly acidic water (pH less than 7) slowly wears down rock.
What kind of rock is eroding cliffs in Arizona?
SANDSTONE cliffs eroding in Arizona.
By what is weathering/collapse cliff in Dover England?
WEATHERING/COLLAPSE of a LIMESTONE
(SEDIMENTARY rock) cliff in Dover, England.
Caused by frost. Frost causes rocks to fracture.
When rain absorbed by LIMESTONE surface
freezes, it exerts pressure on the rock
below, fracturing it.
What is soluble?
a substance is said to be “SOLUBLE” when it can DISSOLVE/become incorporated into a liquid such as water.
How does dissolution form?
➢ form of WEATHERING wherein water, generally slightly acidic water (with a pH less than 7) slowly wears down rock/minerals.
➢ process by which SOLUBLE ROCKS/MINERALS (i.e., rocks/minerals that can DISSOLVE/become incorporated into water) are in fact dissolved/incorporated into water due to the passage of water over the rock surface, entry of water into rock fractures or entry of water into rock pores.
➢ DISSOLUTION faster in more SOLUBLE ROCKS/MINERALS and slower in less SOLUBLE ROCKS/MINERALS.
In Italy and in America what happens?
DISSOLUTION of LIMESTONE (Italy) right and DISSOLUTION of DOLOSTONE (cave in Arizona) by slightly acidic groundwater
below.
Which ROCKS/MINERALS are soluble/experience DISSOLUTION?
LIMESTONE (rock) consisting of CALCITE (mineral made up of calcium carbonate, CaCO3)
DOLOSTONE (rock) consisting of DOLOMITE
(mineral made up of calcium magnesium carbonate,
CaMgCO3)
GYPSUM (rock or mineral) consisting of calcium
sulfate, CaSO4 or CaSO4·2H2O)
HALITE (mineral) consisting of sodium chloride
(NaCl)
GYPSUM is more soluble than LIMESTONE and
DOLOSTONE.
HALITE is very SOLUBLE and therefore only exists
in dry environments.
What do erosion, weathering and dissolution create?
create raw materials for making new
SEDIMENTARY ROCKS.
Using these raw materials (namely, smaller rocks and
SEDIMENT/UNCONSOLIDATED MATERIALS such
as gravel, sand, silt, clay), new minerals and new
rocks are generated by LITHIFICATION.
What is lithification?
➢ from ancient Greek word “LITHOS” meaning “rock”.
➢ divided into two distinct processes, COMPACTION and CEMENTATION.
What is clast?
CLASTIC ROCKS (e.g., CONGLOMERATE) are rocks composed of broken pieces of other rocks bonded together.
CLAST: a fragment within CLASTIC ROCK.
What is compaction?
➢ process by which SEDIMENT/UNCONSOLIDATED
MATERIALS and remains of plants/animals (e.g.,moss,
mollusk shells) become COMPACTED/packed down by
weight of sediment/unconsolidated materials piled on
above them.
What is cementation?
➢ water moving through grains/CLASTS in COMPACTED
materials leaves behind MINERAL CRYSTALS
➢ MINERAL CRYSTALS stick/cement/bond
COMPACTED materials together.
➢ COMPACTING/compressing eventually results in
release of any water and COMPACTED layer of
sediment becomes rock.
What is precipitation?
process by which water rich in
molecules that make up MINERALS/ROCKS gradually
evaporates, allowing molecules to deposit and form
MINERAL CRYSTALS/ROCKS.
This can occur when a lake dries up over thousands of
years as occurred in California’s Death Valley.
What did water leave behind in Death Valley?
➢ halite (NaCl)
➢ calcite (CaCO3)
➢ gypsum (CaSO4 or CaSO4·2H2O)
➢ borax (Na2B4O5(OH)4·8H2O)
In what two categories can sedimentary rocks be classified?
➢ DETRITAL SEDIMENTARY ROCK
➢ CHEMICAL SEDIMENTARY ROCK
What is detrital sedimentary rock?
➢ can consist of ORGANIC and/or INORGANIC materials
➢ formed from ERODED/WEATHERED rock fragments,
smaller rocks, SEDIMENTS/UNCONSOLIDATED
MATERIALS, organic materials.
➢ all aforementioned “ingredients are referred to as
DETRITUS, hence the name DETRITAL SEDIMENTARY
ROCK
➢ DETRITUS is LATIN for WORN DOWN
What does detail sedimentary rocks include?
➢ CONGLOMERATE
➢ BRECCIA
➢ SANDSTONE
➢ SILTSTONE
➢ SHALE (i.e., MUDSTONE)
What can detrital sedimentary rock can consist of?
ORGANIC and/or INORGANIC materials.
ORGANIC DETRITAL SEDIMENTARY ROCK consists of
animal/plant parts (ORGANIC MATERIAL) that decay in
ground.
Over thousands or millions of years, ORGANIC MATERIAL
undergoes COMPACTION and CEMENTATION
(LITHIFICATION), forming rock.
One example (that does not undergo complete
LITHIFICATION) is PEAT, a SEDIMENTARY material
largely consisting of partially decayed vegetation/organic
material such as PEAT MOSS.
Formation of PEAT is first step in forming another important
and controversial ORGANIC SEDIMENTARY MATERIAL.
