rock
coherent, naturally occurring solid, consisting of an aggregate of minerals
stone
a rock used as a construction material
crystals
have crystal faces evident and grew into present shape
grains
fragment of mineral, rock, or glass; no crystal faces
lithification
rockification"; the formation of a rock
sediment
a collection of grains that have grouped together into a coherent mass
cement
precipitation from water that holds grains together
hand specimen
sample that can fit into a person's hand
clastic
designates a rock held together by cement
crystalline
designates a rock whose crystals interlock (nonclastic)
rock classification
the placing of rocks into certain categories based on their physical and chemical properties; proposed by James Hutton in the 18th century as "genetic classification" because it focuses on rock genesis
igneous rocks
formed by the solidification of magma
sedimentary rocks
formed by the cementing together of fragments of pre-existing rocks or precipitation of crystals out of water
metamorphic rocks
formed by the transformation in the solid state of pre-existing rocks by a change in temperature and/or pressure
equant
having similar diameter throughout (e.g. cubic or spherical)
inequant
uneven; having inconsistent diameters throughout
composition
chemical makeup; doesn't have complete impact on mineralogy since temperature and pressure also play a role
texture
the way the grains interact with each other and whether or not inequant grains are aligned parallel to each other
layering
caused by bands of different compositions or textures, or by the alignment of inequant grains
bedding
layering of sedimentary rocks
foliation
layering of metamorphic rock
study of rocks
study of outcrop in the field; take a hand specimen for study using a hand lens and for back in the lab; make a thin section (30 micrometers) and study under a petrographic microscope (polarizing light); take a photomicrograph; can use either microcrobe t
analytical techniques in the study of rocks
Mineral: SIMS, EMP, XRD.
Whole Rock: XRF, AA, ICP-MS, ICP-OES, NAA.
intrusive rock
igneous rock formed by the slow cooling of magma under ground, producing a small number of large crystals (e.g. granite, diorite, gabbro
extrusive rock
igneous rock formed when erupted magma cools quickly on the surface, producing a large number of small crystals (e.g. basalt, andesite, rhyolite)
weathering
process that turns high-temperature minerals to low-temperature ones stable at the Earth's surface; a group of destructive processes that change physical and chemical character of rocks at/near the Earth's surface; forms sediment and soil
erosion
transport (e.g. by wind, ice, gravity) away from the weathering site; this exposes intrusive igneous rock and the process continues
weathering & erosion
how the hydrologic cycle interacts with geology
joints
natural cracks that form in rocks due to the removal of over burden or due to cooling, etc.
talus
accumulation of broken blocks of rock
causes of mechanical/physical weathering
pressure-release (exfoliation), precipitation of crystals, root systems, abrasion, animal attack, temperature changes, frost-wedging, frost heaving
pressure-release
often called exfoliation; caused by unroofing of deep-seated rocks by erosion - sheet joints and joint sets form
precipitation of crystals
salt precipitating from water in crevices/cracks; forces the opening wider
root systems
weathering is dominant in cold/dry climates
abrasion
friction/impact during transport
animal attack
burrowing, mining, etc. opens up pathways for weathering
temperature changes
caused weathering through differential expansion (deserts, mountains, and forest fires); frost wedging in colder climates
frost-wedging
water expands by 9% upon freezing; most significant in areas with frequent freeze/thaw cycle
frost heaving
cooler under rocks, freezes first, expands and lifts
chemical weathering
weathering that affects the chemical properties of a substance; occurs through four main processes: dissolution, hydrolysis, oxidation, and hydration
surface area
ties to mechanical weathering as surface area increases with fragmentation
saprolite
rotten rock produced by chemical weathering in warm, wet climates
dissolution
breaking apart of a rock through chemical weathering
hydrolysis
addition of OH-
oxidation
addition of oxygen
hydration
addition of water
carbonization
addition of CO2
chemical weathering by organisms
Roots, fungi, and lichen secrete organic acids to extract nutrients.
Bacteria can literally eat minerals - have been found several kilometers within the Earth and within solid rock
Bowman reaction series
(1) Discontinuous: Olivine - Pyroxene - Amphibole - Biotite - Quartz, Muscovite, K-feldspar
(2) Continuous: Plagioclase - Quartz, Muscovite, K-feldspar
Olivine [(Mg,Fe)2SiO4]
weathers very quickly - it is not present in sediments, soils, or sedimentary rocks.
Quartz
very resistant to chemical weathering; it is a major constituent of mature sediments.
typical weathering patterns
Feldspars -> clay minerals, salts (change of structure).
Fe-Mg silicates -> Fe oxides, Mg salts, clay minerals.
Quartz = stable.
acid [chemical weathering]
near volcanoes and runoff from mines
spheroidial weathering
weathers a rock to have rounded edges; attacks from one side on face, two on edge, and three on corner
rock
coherent, naturally occurring solid, consisting of an aggregate of minerals
stone
a rock used as a construction material
crystals
have crystal faces evident and grew into present shape
grains
fragment of mineral, rock, or glass; no crystal faces
lithification
rockification"; the formation of a rock
sediment
a collection of grains that have grouped together into a coherent mass
cement
precipitation from water that holds grains together
hand specimen
sample that can fit into a person's hand
clastic
designates a rock held together by cement
crystalline
designates a rock whose crystals interlock (nonclastic)
rock classification
the placing of rocks into certain categories based on their physical and chemical properties; proposed by James Hutton in the 18th century as "genetic classification" because it focuses on rock genesis
igneous rocks
formed by the solidification of magma
sedimentary rocks
formed by the cementing together of fragments of pre-existing rocks or precipitation of crystals out of water
metamorphic rocks
formed by the transformation in the solid state of pre-existing rocks by a change in temperature and/or pressure
equant
having similar diameter throughout (e.g. cubic or spherical)
inequant
uneven; having inconsistent diameters throughout
composition
chemical makeup; doesn't have complete impact on mineralogy since temperature and pressure also play a role
texture
the way the grains interact with each other and whether or not inequant grains are aligned parallel to each other
layering
caused by bands of different compositions or textures, or by the alignment of inequant grains
bedding
layering of sedimentary rocks
foliation
layering of metamorphic rock
study of rocks
study of outcrop in the field; take a hand specimen for study using a hand lens and for back in the lab; make a thin section (30 micrometers) and study under a petrographic microscope (polarizing light); take a photomicrograph; can use either microcrobe t
analytical techniques in the study of rocks
Mineral: SIMS, EMP, XRD.
Whole Rock: XRF, AA, ICP-MS, ICP-OES, NAA.
intrusive rock
igneous rock formed by the slow cooling of magma under ground, producing a small number of large crystals (e.g. granite, diorite, gabbro
extrusive rock
igneous rock formed when erupted magma cools quickly on the surface, producing a large number of small crystals (e.g. basalt, andesite, rhyolite)
weathering
process that turns high-temperature minerals to low-temperature ones stable at the Earth's surface; a group of destructive processes that change physical and chemical character of rocks at/near the Earth's surface; forms sediment and soil
erosion
transport (e.g. by wind, ice, gravity) away from the weathering site; this exposes intrusive igneous rock and the process continues
weathering & erosion
how the hydrologic cycle interacts with geology
joints
natural cracks that form in rocks due to the removal of over burden or due to cooling, etc.
talus
accumulation of broken blocks of rock
causes of mechanical/physical weathering
pressure-release (exfoliation), precipitation of crystals, root systems, abrasion, animal attack, temperature changes, frost-wedging, frost heaving
pressure-release
often called exfoliation; caused by unroofing of deep-seated rocks by erosion - sheet joints and joint sets form
precipitation of crystals
salt precipitating from water in crevices/cracks; forces the opening wider
root systems
weathering is dominant in cold/dry climates
abrasion
friction/impact during transport
animal attack
burrowing, mining, etc. opens up pathways for weathering
temperature changes
caused weathering through differential expansion (deserts, mountains, and forest fires); frost wedging in colder climates
frost-wedging
water expands by 9% upon freezing; most significant in areas with frequent freeze/thaw cycle
frost heaving
cooler under rocks, freezes first, expands and lifts
chemical weathering
weathering that affects the chemical properties of a substance; occurs through four main processes: dissolution, hydrolysis, oxidation, and hydration
surface area
ties to mechanical weathering as surface area increases with fragmentation
saprolite
rotten rock produced by chemical weathering in warm, wet climates
dissolution
breaking apart of a rock through chemical weathering
hydrolysis
addition of OH-
oxidation
addition of oxygen
hydration
addition of water
carbonization
addition of CO2
chemical weathering by organisms
Roots, fungi, and lichen secrete organic acids to extract nutrients.
Bacteria can literally eat minerals - have been found several kilometers within the Earth and within solid rock
Bowman reaction series
(1) Discontinuous: Olivine - Pyroxene - Amphibole - Biotite - Quartz, Muscovite, K-feldspar
(2) Continuous: Plagioclase - Quartz, Muscovite, K-feldspar
Olivine [(Mg,Fe)2SiO4]
weathers very quickly - it is not present in sediments, soils, or sedimentary rocks.
Quartz
very resistant to chemical weathering; it is a major constituent of mature sediments.
typical weathering patterns
Feldspars -> clay minerals, salts (change of structure).
Fe-Mg silicates -> Fe oxides, Mg salts, clay minerals.
Quartz = stable.
acid [chemical weathering]
near volcanoes and runoff from mines
spheroidial weathering
weathers a rock to have rounded edges; attacks from one side on face, two on edge, and three on corner