Earth Science 2 Flashcards
(199 cards)
1
Q
what is a thalweg?
A
This is the line of lowest elevation within a valley or watercourse. the most navigable channel.
2
Q
What is a pools?
A
These are areas of deep water and greater erosion (energy build-up due to less friction)
3
Q
What are riffles?
A
These are areas of shallow water created by deposition of coarse sediment.
4
Q
What is a point bar?
A
A point bar is a depositional feature made of alluvium that accumulates on the inside bend of streams and rivers below the slip-off slope.
5
Q
What is a river cliff?
A
A cut bank, also known as a river cliff or river-cut cliff, is the outside bank of a water channel (stream), which is continually undergoing erosion.
6
Q
What is. slip-off slope?
A
A slip-off slope is a depositional landform that occurs on the inside convex bank of a meandering river.
7
Q
How are terraces formed?
A
A terrace can be formed as a river cuts deeper into the land. A new, lower floodplain may then be established, leaving part of the former flood plain at a higher level as a terrace.
8
Q
What is the principle of uniformitarianism?
A
Uniformitarian Principle, is the assumption that the same natural laws and processes that operate in our present-day scientific observations have always operated in the universe in the past and apply everywhere in the universe.
9
Q
What are the two ways geologist tell time and date events?
A
Relative dating and absolute dating
10
Q
What is relative dating?
A
This is putting things in relative order (in relation to something else) e.g rock a before rock b rock b before rock c
11
Q
what is absolute dating?
A
This is obtaining a numerical age
12
Q
what is stratigraphy?
A
this is a branch of geology concerned with the study of rock layers and layering (strata)
13
Q
What is strata?
A
This is a layer of sedimentary rock or soil, or igneous rock that was formed at the Earth’s surface, with internally consistent characteristics that distinguish it from other layers.
14
Q
What are some subdivisions of stratigraphy?
A
Lithostratigraphy
Biostratigraphy
Magnetostratigraphy
isotope stratigraphy
15
Q
How old is the earth?
A
Approximately 4.6 billion years old
16
Q
What are geochronological units?
A
Subdivided geological time into intervals of known durations (time units)
17
Q
what are chronostratigraphic units?
A
These refer to rocks deposited during a specific time (time-rock units)
18
Q
state the geological Time scale - geochronologic
A
Eon- Which is made up of Era Era - which is made up of periods Period- which is made up of epochs epochs - which is made up of age age - which is made up of chron chron
19
Q
state the geological Time scale - Chronostratigraphic
A
Rocks deposited in the according time eon - eonothem era - earthem period - system epoch - series age - stage chron - chronozone
20
Q
explain the creation of the time scale
A
The time scale unit durations and organization are irregular but not random they dont represent a set amount of time but instead mark major geologic events in time. the scale was created based on relative dating techniques. later absolute dates were found for the major boundaries in the time scale.
21
Q
Explain the naming for the Phanerozoic eon and its era
A
The Phanerozoic (period of visible life) eon (there are different types of eons) and its era were named after the types of fossils seen in the rocks of this age.
22
Q
Explain the naming of periods
A
Periods were named after the localities where they were first studied or typical lithologies form this area.
23
Q
Explain the naming of epochs
A
Epochs of the cenozoic were named based on the similarity of their fossils to modern forms
24
Q
What are the importances of the stratigraphic principles?
A
fundamental for analysing relationship between strata as well as used to place geologic units and features in relative order.
25
what are Principles of stratigraphy?
```
Original Horizontality
lateral continuity
Superposition
cross-cutting relationships
inclusions
fossil succession
```
26
What is original horizontality?
beds are originally laid down horizontally
27
What is lateral continuity?
Bed extend in all directions until they thin to zero or terminate at the edge of their basin
28
What is superposition?
In an underdisturbed section the older beds underly the younger ones.
29
What are way up structures?
This are structures that help to identify which way is up so that superposition can be applied
30
What are some way up structures?
```
Graded bedding
current bedding
ripple marking
fracture cleavage
amygdaloidal lavas
pillow lavas
geo-petal structures/ fossil spirit levels
```
31
What is graded bedding?
a graded bed is one characterized by a systematic change in grain or clast size from one side of the bed to the other.
Coarser sediments at the base of beds
32
How does ripple marks help identifying way up?
The peaks/crest of the ripples would indicate upwards while the troughs would indicate the bottom
33
What are cross-cutting relationship?
The geological feature that cuts through or intrudes into another unit must be younger than the unit it is cutting
34
what is inclusion?
Inclusions in a rock unit are older than the rock itself
35
What are unconformities?
These are surfaces of erosion or non deposition
36
Types of unconformities?
angular unconformity
nonconformity
disconformity
paraconformity
37
what is an angular unconformity?
This is unconformity across which there is a change in dip. there will be a bent or angled layer and then a flat layer.
38
What is a non-conformity?
This is an erosion surface between non-stratified and stratified rocks.
not all rocks lay so you'll have a rock like granite that doesn't layer and then something happened and the stratified rock will deposit on top and layers of sediments will be there.
39
What is a disconformity?
This is an erosion surface across which there is no change in dip.
rocks are layered in the same direction no change in pattern but still tow different types of rock
40
what is a paraconformity?
This is an unconformity caused by a break in deposition with no evidence for erosion.
basically sediments will be deposited in this area but for whatever reason there is a gap in time in which the sediments top being deposited but then they start again after that gap.
41
what laws of stratigraphy did Nicholas steno make?
Law of superposition
the principal of original horizonaility
the principle of lateral continuity
p.s he also created the laws of constant angles
42
What are geo-petal structures/ fossil spirit levels?
basically this is when sediment will fill up an organism like a shell or a clam and the peel/direction in which it settles will indicate the way up.
43
What re the three divisions that Johann Gottob Lehmann MD recognise?`
surficial deposits
stratified mountains
vein mountains
44
What is karst topography and how is it formed?
A landscape that is characterized by numerous caves, sinkholes, fissures, and underground streams. Karst is a topography formed from the dissolution of soluble rocks such as limestone
45
What are physical surface processes?
Weathering, erosion and deposition.
46
What is weathering?
Weathering is the breaking down of rocks, soils, and minerals through contact with the Earth's atmosphere, water, and biological organisms.
47
what is erosion?
erosion is the action of surface processes like wind, water, or other natural agents that removes soil, rock, or dissolved material from one location on the Earth's crust, and then transports it to another location.
48
What is deposition?
This is a geological process in which weathered material is dumped via Wind, ice, water, and gravity transport previously weathered surface material, which, at the loss of enough kinetic energy
49
What are the different kinds of weathering?
Physical, chemical and biological
50
What is Physical weathering?
This is the disintegration of rock into smaller particles by mechanical processes without any change in chemical composition of the rock
51
What is chemical weathering?
This is the decomposition of rock resulting from chemical alteration and dissolution.
52
What is biological weathering?
Biological weathering is weathering caused by plants and animals. Plants and animals release acid forming chemicals that cause weathering and also contribute to the breaking down of rocks and landforms.
53
what are some types of physical weathering?
Frost wedging, salt wedging, Thermal spalling, Activity of organisms (plant roots), zones of weaknesses (bedding planes, joints)
54
what is frost wedging?
the mechanical disintegration of rock by the pressure of water freezing in pores and along grain boundaries.
55
What is salt wedging?
Salt wedging happens when saltwater seeps into rocks and then evaporates on a hot sunny day. Salt crystals grow within cracks and pores in the rock, and the growth of these crystals can push grains apart, causing the rock to weaken and break.
56
What is thermal spalling?
this is the breaking, cracking, peeling off of rock from intense heats. The rapid changes in temperature causes uneven expansion and contraction within the rock resulting in the development of internal stresses and strains which result in cracking.
57
what are bedding planes?
the surface that separates each successive layer of a stratified rock from its preceding layer
58
What are columnar joints?
These are formed form the cooling of igneous rocks
59
what is a joint?
A joint is a break of natural origin in the continuity of either a layer or body of rock
60
How are columnar joints formed?
They are usually formed from igneous rocks (lava flow). lava cools at the surface and causes specially uniformed contractions forming hexagonal features.
61
what is a joint set?
A joint set is a family of parallel, evenly spaced joints that can be identified through mapping and analysis of the orientations, spacing, and physical properties.
62
What is joint system?
consists of two or more intersecting joint sets.
e.g one set would be only moving in a horizontal direction while the other set would be moving in only vertical direction the intersecting of these two would make. joint system
63
what are the effects of physical weathering?
Smaller rocks
| Increase in surface area where chemical weathering can take place
64
What are types of chemical weathering reactions?
Oxidation, Hydration, hydrolysis, carbonation, dissolution, organic weathering and acid rain
65
what is oxidation?
the breakdown of rock by oxygen in the air or water, often giving iron-rich rocks a rusty-coloured weathered surface. this causing rocks to crumble more easily.
66
What is dissolution?
is the process where a solute dissolves in a solvent to form a solution
67
what is hydrolysis?
Hydrolysis takes place when acid rain reacts with rock-forming minerals such as feldspar to produce clay and salts that are removed in solution.
68
What is the most common weathering products?
clay
69
what are the most common rock forming minerals?
Feldspars
70
What is the hydrolysis chemical reaction process?
feldspar + carbonic acid + water= clay dissolved silica + dissolved K + dissolved bicarbonate
2KAlSi3O8 + H2O → Al2Si2O3 + 4SiO2 + 2K + 2HC03
71
What is a the carbonation chemical reaction process?
Carbon dioxide + water
| CO2 + H2O =H2CO3 ( carbonic acid)
72
Where is carbonic acid formed?
in rainwater and surface groundwater
73
What is carbonation?
this is the dissolution of rocks via carbonic acid which is formed from the mixing of rainwater and carbon dioxide.
74
what are factors that affect the rate of chemical weathering?
```
water and precipitation,
temperature,
duration of exposure,
organic activity,
availability of Co2 and O2,
parent material
```
75
What is spheroidal weathering?
is a form of chemical weathering that affects jointed bedrock and results in the formation of concentric or spherical layers of highly decayed rock.
This is usually because the corners are the first part of the rock to be weathered and eroded. leaving a spherical formation behind
76
what is exfoliation?
This is the peeling away of thin outer layers. this is mainly by chemical weathering through alteration and expansion of feldspars.
77
What does weathering produce?
Regolith, sediment (transported and deposited) and dissolved material carried on surface water and ground water.
78
What are factors affecting stream flow?
Gradient, channel cross section (deep and narrow vs wide and shallow), discharge, Load, roughness of channels beds and banks
79
How to calculate discharge of a river?
Discharge = cross sectional area x velocity
80
what are the kinds of loads in a river?
Bed load
| suspended load
81
What are the different ways load is transported?
Suspension, Traction and saltation
82
What is suspension?
this is the load of the river being suspended and carried away
83
What is traction?
This is the load of the river being roll/ slide along the end of the river
84
What is saltation?
This is bedlam bounces along the bed of the river.
85
What happens further downstream of the river
Gradient and bed load size decreases
width, depth, velocity and discharge increases
huh?
86
What are the kinds of stream erosion?
headward erosion, downcutting, floodplain development and base level
87
What is headward erosion?
is erosion at the origin of a stream channel, which causes the origin to move back away from the direction of the stream flow, and so causes the stream channel to lengthen.
88
what is downcutting?
This is the river eroding deeper into its bed
89
What is floodplain development?
This is the river eroding laterally into its bank.
90
what is base level?
This is the lowest level by which erosion by running water can take place.
91
What are different types of stream channels?
Straight, braided, Meandering
92
What is braiding?
This is when a river's level falls rapidly competence and capacity are reduced and the channel may become choked with material causing the river to braid. (divide into a series of converging and diverging segments.)
93
what is a delta?
is a landform created by deposition of sediment that is carried by a river as the flow leaves its mouth and enters slower-moving or stagnant water. This occurs where a river enters an ocean, sea, estuary, lake, reservoir, or another river that cannot carry away the supplied sediment.
94
What is a Yazoo stream?
A Yazoo stream is a geologic and hydrologic term for any tributary stream that runs parallel to, and within the floodplain of a larger river for considerable distance, before eventually joining it
95
What is a bluff?
A bluff is a type of broad, rounded cliff. Most bluffs border a river, beach, or other coastal area. Bluffs may form along a river where it meanders
96
What is a levees?
this is a small natural embankment that is formed when a river overflows its banks the increase in friction causes material to be deposited.
97
What I s a backswamp?
is a type of depositional environment commonly found in a floodplain. It is where deposits of fine silts and clays settle after a flood.
98
What is an alluvial fan?
An alluvial fan is a triangle-shaped deposit of gravel, sand, and even smaller pieces of sediment, such as silt. and are usually created as flowing water interacts with mountains, hills, or the steep walls of canyons.
99
what are terraces?
this is when gradual downcutting and movement of the river leaves abandoned floodplains
100
What is rejuvenation?
occurs when the river's base level falls (i.e. when sea level falls). This can be a consequence of either a fall in the amount of sea water or the land rising.
101
What are the types of incised meanders?
Ingrown and entrenched
102
what is an entrenched meander?
This is the very rapid incision by the river of the sides of the river being resistant to erosion while the bed isn't.
103
What is an ingrown meander?
This is when either uplift of the land or incision by the river is less rapid allowing the river time to shift laterally and to produce an assymetrical cross valley shape.
104
What I s drainage basin?
This is an area of land that is drained by a river and its tributaries
105
What I s a drainage divide?
this is a region or ridge of upland separating drainage basins
106
What is stream piracy?
this is when one river erodes into another river essentially capturing that channel and this is done by headward erosion.
107
What are the different types of drainage types/patterns?
Radial, Trellised, parallel, dentritic
108
Describe dendritic drainage pattern/type.
This is shaped like a tree
109
Describe Radial drainage pattern/type.
This is usually from a high mountain/hill peak and it runs down like the spokes of a wheel
110
Describe Parallel drainage pattern/type.
rivers and tributaries flow downhill parallel to each other
111
Describe Trellised drainage pattern/type.
In areas of alternating resistant and less resistant rock tributaries will form and join the main river at right angles.
112
what is mass wasting
Mass wasting is the movement of rock and soil down slope under the influence of gravity. e.g landslides, landslips, mass movement, soil creep,
113
What are the factors controlling mass wasting?
Gradient (angle of repose), material structure and composition, Fluid content, vegetation, earthquakes, precipitation
114
Explain angle of repose
particles dropped in a pile create an angle of repose base on their size and angularity. Fine sands have. shallower angle of repose that coarse sands and coarse sands have a shallower angle of repose than angular particles.
115
Explain cohesion with water content in soils
Damp sand is the most cohesive while dry sand is less cohesive but saturated sand is less cohesive than them all.
this is because the surface tension in damp sand binds to particles so they resist . While dry sand is only bound by their size and friction with one another. saturated sand are saturated by water which acts as a lubricant.
116
what are the Factors that classify mass wasting?
coherence - Slope failure (coherent masses)
- flows (incoherent chaotic movement)
Composition - Rock, sédiment or debris
Earth Contact - Free-fall or in contact with substrate
Water content
117
Describe slope failure -falls
```
Free fall of rock or sediment.
very rapid.
usually doesnt affect large area.
very steep slopes.
leaves obvious scar and talus below.
```
118
What is a talus?
as the pile of rocks that accumulates at the base of a cliff, chute, or slope.
119
Describe slope failure -slump
```
Coherent mass of rock or sediment or both
Slide along curved rupture surface
Slow to moderate speed
Slumps often move as multiple units
Toes of slump usually an incoherent flow
```
120
What is a scar?
A scar is the area where it is evident that soil has been eroded or torn from this area
121
What is a toe?
A toe is where a mass has over slid usually from a scar and makes a lump
122
Describe slope failure -slide
Coherent mass of rock or sediment or both
Rapid
Slide in contact with substrate as a ~coherent unit
123
What are the types of slope failures?
slump, slides and falls
124
Describe flows - creep
Incoherent mass of rock, sediment, soil, debris
Slow
gradual downslope movement
125
Explain downslope movement related to freeze thaw
As freezing occurs the boulder is raised perpendicular to the ground surface which also rises when the ground thaws and settles gravity pulls the stone down vertically giving it a small but significant down slope movement
126
Describe flows - earth flow, mudflow, debris flow
Incoherent masses
Rapid
distinguished by water content often triggered by rain
mudflow and debris usually more extensive and dangerous
127
Describe flows - lahars
The volcanic eruption melts the snow and ice and that mixes with the ash.
Volcanic mudflow
Water mixes with unconsolidated ash and rock at volcano peak.
Volcanism can cause snow melt
Seismicity associated with volcanism can trigger flow
Can be very rapid and extensive Dangerous
128
List different types of flows
Rock avalanche, debris avalanche, solifunction, lahar, debris flow, earth flow, mudflow, soil creep
129
What are the effects of mass movement
Sediment transport and slope change
130
What are the causes of mass movement?
Oversteepening,
adding mass at the top of the slope
deforestation
oversaturation
131
What are some solutions for mass wasting?
cutting slope, reforestation, dewatering, barrier construction (rock net, cement cover, retaining wall with drainage)
132
What re the types of currents?
Surface currents and deep ocean currents (thermohaline currents)
133
what are tides?
are the rise and fall of sea levels caused by the combined effects of the gravitational forces exerted by the Moon and the Sun, and the rotation of the Earth.
134
Describe spring tides?
This is when the moon and the sun is on the same side of the earth
135
Describe neap tides.
This is when the sun earth and moon create a right angle
136
How are waves created?
Waves are created from the transfer of energy from the wind lowing over the surface of the sea,
137
What happens to a wave in shallow water?
when the depth is less than one-quarter of the wave length, as the water depth decrease so does the wave length. the base of the wave wave slows down and the circular oscillation gets a more elliptical shape. Height and steepness of the wave increase until the upper part spills/ plunges over
138
What is swash and backwash?
Swash is a heavy deposition but weak erosion and backwash is weak deposition but heavy erosion.
139
What is. swell?
waves that formed from distant storms and are travelling distances.
140
What is sea?
Theses are waves that result form local winds and only travel short distances.
141
What is fetch?
This is the maximum distance of open water over which wind can blow.
142
what is the coast?
Coast is the narrow zone where land and sea overlap nd directly interact.
143
What is a storm surge?
This is a rapid rise ins ea level caused by intense areas of low pressure. depressions and tropical cyclones.
144
what are storm tides?
This is when a storm surge and high tide happen at the same time.
145
What is wave refraction?
This is when waves approach an irregular coastline and become increasingly parallel to the coastline.
146
what are some factors that influence shoreline features?
currents, tides, waves, shoreline composition (rocky, sandy), Local Tectonics and Earth Movement uplift & subsidence, global rise and fall of sea level, depth of sea, length and direction of fetch, configuration of coastline, beach morphology.
147
What are some processes of coastal erosion?
Subaerial, wave pounding, hydraulic pressure, abrasion/corrasion, attrition, corrosion/solution
148
what are some coastal erosion landforms?
Headlands, bays, wave cut platforms, caves, blowholes, blowholes, arches, stacks
149
What are the areas of a sandy beach (furthest to nearest)
Offshore, foreshore, backshore, dune belt
150
What are some sandy shoreline features?
barrier islands, spits, bars, beaches, reefs, lagoons.
151
What are clastic beaches shoreline features?
barrier islands, spits, bars
152
What are carbonate beaches shoreline features?
beaches, reefs, lagoons.
153
What is the difference with a clastic beach and a carbonate beach?
A clastic beach is made up of larger particles like pebbles shingle and stuff like that while carbonate beach is much more sandy.
154
What is a spit?
A spit is an extended stretch of beach material that projects out to sea and is joined to the mainland at one end. formed by longshore
155
What is a tombolo?
a bar of sand or shingle joining an island to the mainland.
156
What is a bar
This is when a spit develops across a bay and manages to connect the two headlands.
157
What is a barrier island
This is formed when a a bar is cut off from the main land creating a island that is parallel to the coastline.
158
How are coral atolls formed?
This is when an island continues to subside meanwhile the reef stays and eventually the island disappears.
159
What are some features of emergent shorelines?
Terraced coastlines, raised sea cliffs, raised wave cut beaches, raised reefs, raised sea level notches, marine platforms,
160
What are some features of submergent shorelines?
Sea level rise or land subsidence Irregular embayed coast Drowned valleys
Drowned beaches
Drowned reefs
161
what are the functions of wind?
Erosion, transport, deposition
162
What re the different kinds of wind transport?
Suspension, Saltation (bouncing), Surface creep (rolling)
163
What is a ventifact?
This is a rock that has been abraded, pitted, etched, grooved, or polished by wind-driven sand or ice crystals.
164
what is sand blasting?
s the operation of forcibly propelling a stream of abrasive material against a surface under high pressure to smooth a rough surface
165
what is an Eddie?
An eddy is the swirling of a fluid and the reverse current created when the fluid is in a turbulent flow regime
166
What is plastic flow?
This is when ice at the base of the glacier is frozen to the bedrock or soil therefore the rate of movement decreases as you go down to the base
167
What is basal slip?
this is when pressure of overlying ice melts at the glacier's base the layer of water acts as a lubricant allowing the entire glacier to skate along its base.
168
What are some kinds of glacial erosion?
```
Plucking
Grinding
Abrasion
Carves deep v-shaped valleys
Smoothes continental landscapes
```
169
what are some karst features?
Closed depressions (sinks), conical hills, cockpit karst, poor surface drainage, disappearing or losing streams, spring, caves,
170
What is correlation?
refers to the methods by which the age relationship between various strata of Earth's crust is established
171
what is lithostratigraphy?
this is the correlation of rocks of similar lithology and stratigraphic positions.
172
What are the lithostratigraphic units?
```
Supergroup
Group
Formation - primary unit, mappable
Member
Bed
```
173
What are some lithostratigraphic unit formations?
```
smallest mappable or traceable unit
all mapped rock units must be in a formation
vary in extent and thickness
have a particular position in succession
may also somewhat vary in lithology
```
174
What is a facies?
is a body of rock with specified characteristics, which can be any observable attribute of rocks, and the changes that may occur in those attributes over a geographic area.
175
What is transgressions?
transgression is a geologic event during which sea level rises relative to the land and the shoreline moves toward higher ground, the layers of soil will shift and this results in a slanted rock layers (deposits lithostratigraphic units in different places at different times.
176
what are diachronous units?
in different geological periods. done by transgression
177
What did Giovanni Arduino develop/ invent?
He divided Earth history into three orders:
Tertiary (montes terziarii) – unconsolidated sedimentary rocks many fossils overlain by volcanic rocks.
Secondary (montes secondarii) – hard sedimentary rocks with fossils
Primitive (montes primiarii) – a lower division of schists overlain by an upper division calcareous and sandy rocks.
178
what theory did Abraham Werner and the Neptunists
| invent?
In the Neptunist Theory, basalt and granite were formed by precipitation from an ocean.
179
What is Werner's classification?
Werner recognised five principle rock formations
1. Volcanic Series
2. Alluvial or Tertiary (Aufgeschwemmte) Series
3. Secondary or Stratified (Flötz) Series
4. Transition (Ubergangsgebirge) Series
5. Primitive (Urgebirge) Series
180
What theories did James Hutton state?
1st, That the land on which we rest is not simple and original, but that it is a composition, and had been formed by the operation of second causes.
2nd, That before the present land was made, there had subsisted a world composed of sea and land, in which were tides and currents, with such operations at the bottom of the sea as now take place.
therefore.
1st, The consolidation of masses formed by collections of loose or incoherent materials;
2ndly, The elevation of those consolidated masses from the bottom of the sea, the place where they were collected, to the stations in which they now remain above the level of the ocean.”
181
explain Hutton and the origin of granite
Hutton found granite penetrating metamorphic rocks (schists) and theorized that the granite had once been molten and had formed from the cooling of molten rock. So the granite must be younger than the schists.
182
What is the Law of Cross Cutting Relationships by James Hutton?
states that
if a fault or other body of rock cuts through another
body of rock then it must be younger in age than the
rock through which it cuts
183
what are Jean-Baptiste Lamarck main themes on evolution?
Animals adapt to the needs of their local environments.
Individuals lose characteristics they do not require (or use) and develop characteristics that are useful.
Inheritance of acquired traits – Individuals inherit the traits of their ancestors.
Animals change from simple to complex forms over time.
184
what are Georges Cuvier views on evolution?
that one fossil form does not
gradually change into another form, and he objected to
any notion of evolution as proposed by Lamarck.
Instead, he proposed that species appeared abruptly in the fossil record and persisted unchanged until they became extinct ("punctuated equilibrium").
Cuvier proposed that fossils had been destroyed by some kind or series of catastrophies
185
what is William Smith law of final succession?
each stratum contained organized fossils peculiar to itself, and might, in cases otherwise doubtful, be recognized and discriminated from others like it, but in a different part of the series, by examination of them. “
186
What theory did Sir Charles Lyell invent?
he devised four intervals:
Pleistocene (originally newer Pliocene) – most recent (90% living molluscs)
Pliocene (originally older Pliocene) - more of recent (33 to 50% living molluscs)
Miocene - less of recent less than 18% living molluscs)
Eocene - dawn of recent (0.5 to 3% living molluscs)
187
what theories did Charles Darwin invent?
Evolution of Coral Reefs.
Natural Selection
theory of evolution
188
How to classify rocks?
Stratigraphy
Lithostratigraphy
Biostratigraphy
Chronostratigraphy
189
What is Stratigraphy?
This is the classification of the rock strata (typically stratified rocks such as sedimentary rocks and volcanic rocks).
190
what is Lithostratigraphy?
Lithostratigraphy is a classification of rocks based on their lithological (physical and petrographic) characteristics.
191
what is Biostratigraphy?
This is the classification of rocks based on the fossils they contain. Rocks are divided into ‘zones’ based on their fossils
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what is Chronostratigraphy?
Chronostratigraphy is the division of geological time into distinct time intervals.
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What should each lithostratigraphic unit contain
A Description – The lithological characteristics of the unit.
A Type Locality – The locality after which the unit is named where the unit is well exposed.
Its Age – relative (in terms of its relation to other units) or absolute (in terms of millions or billions of years).
The Thickness of the Unit.
The Nature of it Boundaries with other units.
e.g “The Guys Hill Formation is a thick unit of quartz-rich sandstones and mudstones,with a thickness of between 150 and 300 m. The type locality is situated at Guys Hill in St. Catherine. The basal boundary is an unconformity, and the upper boundary is conformable with the overlying Chapelton Formation. The fossils it contains indicates it is of Eocene age.”
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what re some examples of Lithostratigraphic Correlation – marker beds?
Bentonites or volcanic ash beds.
Boloide (meteorite) impact clays bands (e.g., end of the Cretaceous)
Distinctive sedimentary beds
Varves (annual layers in lacks)
Chert or flint (silica) layers
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What are the different kinds of fossils?
Macrofossils, microfossils, nannofossils, trace fossils
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What are macrofossils?
Large fossils that can be seen with the naked eye (the term Mesofossils has been used for fossils in the size range 1 to 4 mm). They may be preserved as impressions (moulds), casts or as original material.
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What are microfossils?
These are small fossils that can be seen with the aid of a microscope. They include groups such as foraminifers, ostracods, and radiolarians. Many sedimentary rocks contain thousands of microfossils even in a small sample.
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What are nannofossils?
Fossils that can only be seen with aid of a Scanning Electron Microscope.
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What are trace fossils?
These are the traces left by the activities of animals and include trails, track ways and burrows.
