Geology Test Questions

1. The outer core of the earth is solid, and the inner core is liquid (true,false)
false
2. The core of the earth is thought to be composed mostly of
iron
3. The earth’s mantle is composed mostly of
olivine
4. The composition of the earth’s mantle is closest to
(Mg,Fe)2SiO4
5. The weight percentage of iron in the whole earth is greater than its percentage in the earth’s crust(true,false)
true
6. The oceanic crust is denser than the continental crust because it richer in iron(true,false)
true
7. The average thickness of the earth’s oceanic crust is closest to
10 km
8. The name of the meteoritic rock type that is thought to represent the composition of the earliest, most primitive whole earth is
chondrite
9. Among the types of chemical bonds, which produces the strongest bond?
covalent
10. Among the types of chemical bonds, which one produces compounds that are soluble in water?
ionic
11. Which of the following conditions is not a necessary part of my definition of a mineral?
inorganic
12. The word that best describes how minerals grow is
accretion
13. Which mineral group is most abundant in the earth’s crust?
feldspar
14. The longer the length of a chemical bond, the weaker that bond is(true,false)
true
15. The brittle region of crust and upper mantle that surrounds the earth is called the
lithosphere
16. Crystals tend to grow fastest at their
corners
17. The temperature at the earth’s center is actually higher than that predicted by the crustal geothermal gradient(true,false)
true
18. The average geothermal gradient through the earth’s crust is
20C/km
19. The average geobaric gradient through the earth’s crust is
333bar/km
20. The smallest portion of a mineral that contains all of the chemical and structural information needed to reproduce the mineral in three dimensions is referred to as
unit cell
21. Is the following relative hardness among these minerals correct
calcite < fluorite < corundum?:yes
22. The weak and ductile region in the mantle is called the
asthenosphere
23. The amphiboles and micas are different from most other rock-forming minerals because they contain
H2O
24. The process that is thought to be closely linked with the movements of the lithospheric plates is
convection in the mantle
25. Other than silicon (Si), what three cations (positively charged ions) comprise the pyroxenes?
Ca, Fe, and Mg
26. Anorthite, albite, and orthoclase belong to what mineral family?
Silicate
27. The composition of albite is expressed as
NaAlSi3O8
28. How (by what method) is the crystalline structure of minerals determined?
x-ray diffraction
29. On the basis of total volume of rock, where is most of the earth’s heat generated?
Mantle
30. According to the estimate cited in class, approximately how much of the earth’s heat output is primordial; that is, is left over from the earliest stages of the earth’s formation?
20%
31. In crystalline materials, most of the unsatisfied electrical charge is concentrated at
corners
32. Minerals of a group share the same general chemical formula and the same crystal structure(true,false)
true
33. Calcite is the principal mineral in what rock type?
limestone
34. Mineral species are represented by a unique chemical formula because they usually occur as pure, end-members that match that formula quite well(true,false)
false
35. In mineralogy, a measure of the tendency of a mineral to hold together when struck with a blow or stressed by pressure is
tenacity
36. The lithosphere of the earth includes
crust and mantle
37. When bonded atoms are pushed closer than their normal bond distance, then they begin to repel one another because of
the charge of their protons
38. The elements carbon (C) and silicon (Si) possess similar chemical properties because
they lie in the same column of the periodic table
39. As far as you know at this point, the mean (average) density of the earth’s lithosphere is lower than the mean (average) density of the asthenosphere(true,false)
true
40. Diamond and graphite are as different as two minerals can be. The difference in their physical properties stems from their very different
crystal structures
41. A substance is classified as metamict if
its crystal structure has been destroyed by ionizing radiation
42. The type of tectonic boundary where one piece of lithosphere goes down beneath another is called
a subduction zone
43. The special type of linear valley that develops at the center of a divergent plate boundary is called
a rift
44. Which type of tectonic boundary offsets segments of the oceanic ridges, resulting in a zig-zag, or stitch-like pattern of the oceanic ridges segments?
a transform
45. The highest mountain belts in the world are created by
continental collision
46. The average geobaric gradient of the earth (rate of increase in pressure with depth) is greater than the geobaric gradient in the earth’s crust(true,false)
true
47. The thickest crust found on earth today lies beneath
the Himalaya Mountains
1. H2O under high pressure lowers the melting temperature of most rocks(true,false)
true
2. A dense cloud of hot ash and gases that descends rapidly down the slopes of some volcanoes is termed
an ignimbrite
3. In general, the last mineral to disappear upon complete melting of a rock will be the first mineral to appear upon crystallization of that melt(true,false)
true
4. Which of the following minerals is not normally present in granite?
pyroxene
5. Which of the following minerals is not normally present in gabbro?
quartz
6. The intrusive equivalent of an andesite is
diorite
7. Among the rocks below, which one would be considered most mafic in composition?
basalt
8. Among the rocks below, which one would be considered most sillceous in composition?
rhyolite
9. The name of the rock type that constitutes most of the earth’s mantle is
peridotite
10. The process of igneous intrusion (upward ascent) by which a block of overlying rock that is surrounded by melt and subsequently sinks into the magma chamber is called
stoping
11. Granite is more abundant that its volcanic equivalent because of what properties of granite-forming magmas?
high silica, high viscosity
12. The viscosity of rhyolitic melt is higher than that of basaltic melt(true,false)
true
13. In general, magmas of the composition of basalt erupt more violently and explosively than do those of andesite(true,false)
false
14. The process most closely linked with the eruption of lava at the earth’s surface is
vesicultaion of gases or crystal settling
15. In general, rocks begin to melt at temperatures lower than the melting temperature of any individual mineral in the rock(true,false)
true
16. In general, the compositions of natural melts are fairly close to the eutectics of the rocks from which they originate(true,false)
true
17. The best definition of “eutectic” is
the composition of melt at the solidus for a particular assemblage of minerals
18. Shield volcanoes form mostly from lavas of the composition of
basalt
19. The classic shape of composite volcanoes, such as Mt. Fujiyama, is derived mostly from magmas of what composition?
andesite
20. Magma that solidifies in vertical cracks and conduits forms igneous rocks that are referred to generally as
dikes
21. Crystal settling is important for the separation of crystals and magma in what magma type?
basaltic
22. In general, the more H2O that is dissolved in a magma, the higher its viscosity will be (all othercfactors of pressure, temperature, and melt composition as constants)(true,false)
false
23. Magmas of very high viscosity are more likely to form
plutonic rocks
24. At the initial instant of eruption of andesite volcanoes, the gases and particles are expanding at the rate of about twice the speed of sound(true,false)
true
25. The first stage of eruption in a typical basalt volcano forms
a cinder cone
26. The first stage of eruption in a typical andesite volcano forms
a base-surge debris cloud
27. The melting temperature of continental crustal rocks crosses the geotherm at approximately what temperature and depth?
800C, 30 km
28. The melting temperature of peridotite crosses the geotherm at approximately what temperature and depth?
1800C, 100 km
29. An element is defined as incompatible if it is
concentrated in melt over crystal
30. An element is defined as volatile if it is
concentrated in vapor over crystal
31. During the process of fractional crystallization, incompatible elements are concentrated in
melt
32. Among the elements or compounds below, which pair possesses the most compatible behavior?
Fe and Mg
34. On the basis of equal volumes of rock, peridotite and continental crust can generate about the same proportion of granitic magma because the peridotite melts at higher temperature than the continental crust (true,false)
false
1. This depositional environment is characterized by channel sands and broad, flat
deposits of silt distributed laterally on either side of the channel sands
fluvial planes and lowlands
2. This depositional environment is characterized by coarse gravels and economic deposits of dense minerals
fluvial mountainous terranes
3. An economic deposit formed entirely by a sedimentary process is known as a(n)
placer
4. This depositional environment is characterized by a mixture of abundant fine-sand, silt
and the fossil shells of marine animals that thrive in shallow tidal areas
lagoon
5. This depositional environment is composed almost entirely of the cemented remains of animal shells
reef
6. This depositional environment is characterized by finely-laminated black clay, with layers of chert and occasional lenses of submarine debris flows
deep marine
7. This depositional environment is characterized by well-sorted and well-rounded quartz
sand
beach
8. Submarine debris flows form a deposit known as a(n)
turbidite
9. In a water suspension, clay minerals tend to be transported farther than quartz clasts of the same weight(true, false)
true
10. In general, which of the following properties of ordinary silicate rock or mineral clasts is the most important factor affecting sediment sorting and transport in streams
clast size
11. The density of average silicate rocks and minerals is closest to
2.5-3.5gm/cc
12. The grain size of sediment deposited generally decreases as the topographic slope
decreases (true,false)
true
13. The volume of sediment deposited generally decreases as the topographic slope
decreases (true,false)
false
14. Which of the following minerals is a common sedimentary cement?
mica
15. Which of the following minerals is a common sedimentary cement?
iron oxide
16. In a marine delta, the contact between topset and foreset deposits is a useful indicator of
former sea level elevation
17. In a marine delta, the topset deposits are finer-grained than the foreset deposits (true, false)
true
18. In a marine delta, the topset deposits are fluvial, whereas the foreset deposits are
marine (true, false)
false
19. Salt diapirs originate from
evaporites
20. The majority of sediment is deposited
in marine environments
21. A sedimentary rock formed by the lithification of pebbles would be called
conglomerate
22. Most stream sediment is deposited during periods of increasing flow velocity(true,false)
false
23. A typical product of the weathering of feldspar is
clay (kaolinite)
24. Chemical weathering occurs because most ordinary minerals are more soluble in neutral solutions than in acidic solutions (true,false)
false
25. The volume change when water freezes to ice is close to
+9%
26. Plants are important agents of
both chemical and mechanical weathering
27. In the near-surface environment, water gets access to rock via a system of
joints
28. Porosity is a measure of
void space
29. Permeability is a measure of
fluid flow
30. When unconsolidated sediment becomes lithified, porosity normally
decreases
31. If the directional pressures applied to a rock body are such that PX > PY > PZ, then the stress on the rock would be measured by
PX – Pz
32. The term “pressure solution” refers most closely to
enhanced solubility of mineral grains at their points of contact
33. When pressure-solution operates, mineral material is
dissolved in regions of high pressure and deposited in regions of low pressure
34. In their metamorphic cycle, most metamorphosed rocks record
the peak metamorphic condition
35. Foliation in a metamorphic rock is most likely to be expressed by
mica
Figure 1 is labeled with several regions of metamorphism (facies), each of which has a name. In Questions 36-40, associate the different metamorphic conditions with its correct facies name.
36. The metamorphic facies A represents
zeolite
37. The metamorphic facies B represents
greenschist
38. The metamorphic facies C represents
amphibolite
39. The metamorphic facies D represents
eclogite
40. The metamorphic facies E represents
blueschist
41. The protolith of amphibolite is
basalt
42. The protolith of marble is
limestone
43. The protolith of muscovite (mica) schist is
shale
44. Which of the following minerals is NOT a common green constituent of greenschist?
gamet
45. Hydrothermal metamorphism affects approximately what percentage of the oceanic
crust?
80%
46. In a typical magmatic-hydrothermal metal deposit
copper and iron are deposited closest to the source of heat, gold and silver are
farthest from the source of heat
47. During magmatic-hydrothermal contact metamorphism, initially anhydrous minerals are metamorphosed to hydrous minerals (true, false)
true
48. During magmatic-hydrothermal contact metamorphism, elements that may eventually form ore deposits behave in what chemical fashion?
incompatible
49. During prograde metamorphism, the water content of the metamorphic minerals
generally increases with metamorphic grade (true, false)
false
50. During the history of uplift for most metamorphic rocks, retrograde metamorphism does not occur to any appreciable extent (true, false)
true
51. Figure 2 shows a block diagram of two
metamorphic rocks of identical composition. Which
arrow, A, or B, points in the direction of increasing
metamorphic grade?
A
52. A fracture that has been filled with quartz or calcite, and may sometimes include
minerals like galena, sphalerite, and pyrite, is referred to as
a vein
53. Ore deposits formed on the sea floor are referred to by what terms?
black smoke and chimneys
54. Figure 3 shows two mica grains in different orientations with respect to directed
pressures, whose magnitudes are shown by the lengths of arrows. If pressure solution occurs, then the likely result will be
mica A will dissolve and mica B will grow
1. Which period is the oldest jurassic, silurian, permian, cretaceous?
silurian
2. Which period is the youngest jurassic, silurian, permian, cretaceous?
cretaceous
3. Which period is the Cenozoic jurassic, silurian, tertiary, devonian?
tertiary
4. Which period is not in the Paleozoic carboniferous, silurian, triassic, devonian?
Triassic
5. Which eon is the older proterozoic or archean?
archean
6. The lower boundary of the Cambrian is now placed at
542 Ma
7. The Chicxulub meteorite impact occurred approximately how long ago?
65 Ma
8. Which era contains the “age of dinosaurs” proterozoic, mesozoic, paleozoic, cenozoic?
mesozoic
The Figure 1 above shows a schematic geologic map.
9. Which rock is younger, Sedimentary rock or Metamorphic Rock?
gneiss
10. Which fault is younger?
fault a
11. In the radioisotope system of 235U, the daughter isotope is
207 Pb
12. In the radioisotope system of 40K, the daughter isotope is
40 Ar
13. The mineral that is most commonly used to obtain dates based on the uranium-lead method is
zircon
14. The mineral the is most commonly used to obtain dates based on the thorium-lead method is
monazite
15. In radiometric dating, the “decay constant” is
the time required for half of a large population of radioactive atoms to decay to their daughter products.
16. In the radioisotope system consisting of 87Rb, 87Sr, and 86Sr, 86Sr is the
non-radiogenic isotope of the daughter product
17. In the radioisotope system consisting of 87Rb, 87Sr, and 86Sr, 87Sr is the
radiogenic daughter isotope
18. Among the common radioactive isotope systems used for dating geologic events, the one with the shortest half-life is (40K-40Ar, 238U-206Pb, 87Rb-87Sr, 14C-14N)
14C-14N
Figure 2 shows a typical plot of isotope ratios used to deduce the ages of rocks. Questions 19 – 23 pertain to this diagram.
19. In Figure 2, the line defined by the points AED is termed
the isochron
20. In Figure 2, the isotope ratios actually measured in the rocks (some long time after the rocks formed) are denoted by points
C and D
21. In Figure 2, when the rocks in question were first formed, their initial 87Sr/86Sr ratio would have been represented by
A
22. All of the radiogenic daughter isotope contained by the rocks in Figure 2 formed after the rocks crystallized (true, false)
true
23. The slope of the line AED
remains constant
24. The determination of radiometric ages relies on data from what type of instrument?
mass spectronmeter
25. Figure 3 shows a vertical sedimentary sequence. This sequence would reflect
a marine transgresssion
26. Erosional unconformities are most likely to form during periods of
continental subsidence
27. The CO2 content of the Cretaceous atmosphere was high because of
widespread volcanic eruptions
28. In the Cretaceous, tropical forests containing over 100 species of trees per acre extended north and south from equatorial regions almost to the Arctic and Antarctic circles (true, false)
true
29. Which of the following attributes is not desirable in a good index fossil widely distributed across common geologic environments, short-lived in evolutionary time, narrowly restricted to very localized environments, distinctive visual markings?
narrowly restricted to very localized environments
30. The principal use of a facies fossil lies in
defining the environment in which the fossil once lived
31. The extinction of the dinosaurs occurred across what geologic period boundaries?
cretaceous-tertiary
32. Animals with hard shells first appeared in abundance near the beginning of which period?
cambrian
33. The shells of most marine animals (excluding planktonic radiolaria) were and still are composed of
calcite or aragonite
34. Marine animals probably obtained the ability to precipitate shells because of a relatively sudden increase in the amount of what element in their environment?
oxygen
35. The likely source of the element referred to in (34) above was
photosynthesis by blue-green algae
36. Which of the following data sources is not found in the “clay layer” at the Cretaceous boundary?
diamonds
37. The meteorite impact that is thought to have finally extinguished the dinosaurs (or at least hastened their departure) is located at
Chicxulub, Yucatan, Mexico
38. In a normal fault, the rock on the upper side of the fault surface moves
down
39. The tectonic regime or environment in which normal faults are prevalent occurs where
lithospheric plates are under extension
40. The prevalent fault motions in subduction zones are
reverse faults
41. The type of rock motion illustrated in Figure 4 (when viewed in cross section, not map view) that produces (apparent) folds in rocks is termed
passive-slip
42. The type of rock motion illustrated in Figure 5 that produces folds in rocks is termed
flexure-slip
43. Folds are usually developed in regions where rocks are undergoing
compression
44. Earthquakes originate where rocks possess
elastic properties
45. The energy associated with earthquakes is released during
elastic rebound
46. The descriptions of damage and human perceptions that describe the intensity of an earthquake are measured by
the modified Mercali scale
47. The measure of the total energy released during an earthquake is referenced to
the Richter scale
48. The velocity of seismic waves (P or S) increases as the density of rocks
increases
49. P-waves travel faster than S-wave (true, false)
true
50 The mechanical deformation (change of shape or volume) of rock is a measure of
strain
(1) What percentage of the earth’s volume does the crust comprise (constitute)?
2%
(2) What percentage of the earth’s volume does the mantle comprise (constitute)?
82%
(3) What percentage of the earth’s volume does the core comprise (constitute)?
16%
(4) Explain convection
how does it work, and what materials and conditions are necessary for convection to operate?:Mostly vertical transfer of heat and mass caused by density instabilities resulting from hotter, less dense material beneath colder, more dense material. If the medium is fluid, then the density contrast will cause hotter, less dense material to rise, and colder, more dense material to sink in a gravitational field.
key concepts
relations of density to temperature, mass transfer in a gravitational field, heat source from below, fluid (or plastic) medium is necessary.
(1) Which of the following formulas is a correct representation for the composition of olivine?
(Mg,Fe)2SiO4
(2) What is approximate volumetric percentage of oxygen in olivine?
86%
1. From the surface of the earth, the depth to the top (upper surface) of the core is closest to
3000km
2. The lithosphere of the earth includes both crust and mantle (true,false)
true
3. The process by which inanimate objects grow is best described as
accretion
4. Which meteorite class is believed to represent the average composition of the whole earth?
chondrite
5. On average, the crust beneath the ocean basins is thicker than the crust that
comprises the continents (true, false)
false
6. On average, the crust beneath the ocean basins is denser than the crust that
comprises the continents (true, false)
true
7. The principle method by which a substance is determined to be crystalline or
amorphous is termed
x-ray diffraction
8. Most of the mineral families are determined according to their
anions
9. Most of the rock-forming minerals belong to which family?
silicates
10. In general, the shorter the distance of separation between two chemically bonded atoms,
the stronger the bond will be
1. In class, I gave you two pairs of terms that complement those below to describe the textures and emplacement of igneous rock-forming magmas. Complete the table with the four terms in question.(8 pts)(2 pts ea in correct vertical position)
3. Name the three most abundant minerals in granite
quartz, Na-feldspar or plagioclase, alkali feldspar or K-feldspar
4. Name the three most abundant minerals in gabbro
Ca-feldspar or plagioclase, pyroxene or augite, olivine
5. For each “phaneritic” rock on the left, give its “aphanitic” equivalent on the right (gabbro, granite, diorite)
basalt, rhyolite, andesite
6. Magma (liquid) of granitic composition is less viscous than magma of gabbroic
composition (true / false)
false
7. Magma (liquid) of granitic composition is richer in silica than magma of gabbroic composition (true / false)
true
8. Magma (liquid) of granitic composition is more mafic than magma of gabbroic
composition (true / false)
false
9. Magma (liquid) of granitic composition has a lower gas content than magma of
gabbroic composition (true / false)
false
10. Magma (liquid) of granitic composition freezes at a lower temperature than
magma of gabbroic composition (true / false)
true
(1) Magmas of the composition of basalt normally form what type of volcano?
shield
(2) The classic, steep-sided shape of volcanoes like Mt. Fujiyama in Japan are composed
mostly of
andesite
(3) The flows of thin, runny, ropy basalt are referred to as
pahoehoe
(4) In general, eruptions of basalt are more violent than eruptions of andesite (true/false)
false
(5) The process that drives volcanic eruptions is most closely associated with
vesiculation
(6) An ignimbrite is best described as
a dense ash cloud that flows along the ground
(7) The addition of H2O to ordinary rocks at high pressure
lowers their solidus temperatures
(8) The addition of H2O to magmas (molten silicate material) at high pressure does what?
lowers their viscosity
1. A typical product of the weathering of feldspar is
clay(kaolinite
2. This depositional environment is characterized by channel sands and levees, and broad, flat deposits of silt distributed laterally on either side of the channel sands.
fluvial planes and lowlands
3. The volume change when water freezes to ice is close to
+9%
4. An economic deposit formed entirely by a sedimentary process is known as a
placer
5. In a normal graded bed how does the grain size change?
the grain size of sediment increases from top to bottom
6. This depositional environment is characterized by finely-laminated black clay, with layers of chert and occasional lenses of submarine debris flows.
deep marine
7. Submarine debris flows (landslides) form a deposit known as a(n)
turbidite
8. In general, which of the following properties of ordinary silicate rock or mineral clasts is the most important factor affecting sediment sorting and transport in streams?
clast size
9. The density of average silicate rocks and minerals is closest to
2.5-3.5gm/cc
10. The grain size of sediment deposited generally decreases as the topographic slope decreases (true/false)
true
11. The volume of sediment deposited generally decreases as the topographic slope decreases (true/false)
false
12. Which of the following minerals is a common sedimentary cement?
quartz
13. In a marine delta, the contact between topset and foreset deposits is a useful indicator of
former sea level elevation
14. The majority of sediment is deposited in
marine environments
15. Most stream sediment is deposited during periods of increasing flow velocity(true/false)
false
16. Porosity is a measure of
void space
1. The term “pressure solution” refers most closely to
enhanced solubility of mineral grains at their points of contact
2. When pressure-solution operates, mineral material is what?
dissolved in regions of high pressure and deposited in regions of low pressure
3. In their metamorphic cycle, most metamorphosed rocks record
the peak metamorphic condition
4. Foliation in a metamorphic rock is most likely to be expressed by
mica
6. The most likely protolith of amphibolite is
basalt
7. The most likely protolith of muscovite (mica) schist is
shale
8. Contact-hydrothermal metamorphism affects approximately what percentage of the oceanic crust?
80%
9. In a typical magmatic-hydrothermal metal deposit what is normally deposited near what sources?
copper and iron are deposited closest to the source of heat, gold and silver are farthest from the source of heat
10. During magmatic-hydrothermal contact metamorphism, initially anhydrous minerals are metamorphosed to hydrous minerals (true/false)
true
11. During prograde regional metamorphism, the water content of the metamorphic minerals generally increases with metamorphic grade (true/false)
false
12. During the history of uplift for most regional metamorphic rocks, retrograde metamorphism does not occur to any appreciable extent (true/false)
true
13. Submarine hydrothermal vents issuing from the sea floor produce features that are termed
black smokers and chimneys
1. Choose from the formulas at the right and write the letter (a – f) that correctly associates the mineral with its composition (olivine, calcite, magnetite, anorthite, muscovite, orthoclase)
in order-(Mg, Fe)2SiO4, CaCO3, Fe3O4, CaAl2Si2O8, KAl3Si3O10(OH)2, KAlSi308
2. Choose from the rock types on the right and write the letter (a – c) that correctly associates intrusive and extrusive rocks with their respective counterpart of the same composition (diorite, basalt, granite)
in order-andesite, gabbro, rhyolite
3. Choose from the rock types on the right and write the letter (a – b) that correctly associates the correct magma type (basalt or rhyolite) with the properties (more silicic, more mafic, more viscous, more gas content, formed at lower temperature and pressure, formed by partial melting of the mantle)
rhy. is more silicic, bas. is more mafic, rhy. is more viscous, rhy. is more gas content, rhy. is formed at lower temp and pres, bas. is formed by part. melt.
4. Choose from the rock types on the right and write the letter (a – c) that correctly associates the protolith (starting rock) with its likely metamorphic product (amphibolite, muscovite schist, eclogite, slate, marble, blueschist)
in order-basalt, shale, basalt, shale, limestone, basalt
5. In Figure 1, associate the rock type with its probable environment of formation (black shale, limestone, fossil siltstone, orthoquartzite, sand/mudstones)
black shale-a deep marine deposit, limestone-a shallow reef deposit, fossil siltstone-a shallow lagoon deposit, orthoquartzite-a beach deposit, sand/mudstones-a fluvial deposit
6. The depositional sequence in Figure 1 corresponds to what?
a marine transgression
7. Which period is the oldest(jurassic, silurian, permian, cretaceous)?
Silurian
8. Which period is the youngest (jurassic, silurian, permian, cretaceous)?
cretaceous
9. Which period is in the Cenozoic (jurassic, silurian, tertiary, devonian)?
tertiary
10. Which period is not in the Paleozoic (carboniferous, silurian,triassic,devonian)?
triassic
Categories: Geology