chapter 1: earth as a planet
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Chapter 1: Earth as a Planet. What is Geology?. Geology Scientific study of Earth Physical geology Understand processes & materials Historical geology Sequence of geologic events. Using the scientific method. Scientific method How scientists approach problems - PowerPoint PPT PresentationTRANSCRIPT
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Chapter 1: Earth as a Planet
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What is Geology?• Geology
– Scientific study of Earth• Physical geology
– Understand processes & materials
• Historical geology– Sequence of geologic
events
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Using the scientific method• Scientific method
– How scientists approach problems
1. Observations & data gathering
2. Formulating hypothesis• Hypothesis: plausible, but
not proven, explanation for how something happens
3. Testing hypothesis4. Formulating theory
• Theory: hypothesis tested & supported by observation & experimentation
5. Formulating law/ theory
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The Earth system• System concept
– Break large complex items into smaller pieces without losing sight of big picture
– Geosphere • Solid Earth
– Biosphere • All living & once living
organisms– Atmosphere
• Gasses surrounding Earth– Hydrosphere
• All water on Earth– All locations & all states
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Cycles and interactions• Hydrologic cycle
– Describes movement of water
• Rock cycle– Processes that form,
modify, transport or break down rock
• Tectonic cycle– Processes that drive
movement &interactions in lithosphere
– Lithosphere
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Earth in space• The solar system
– Earth is about 4.56 billion years old– Earth is 1of 8 planets orbiting Sun
• Also includes moons, asteroids, comets, meteoroids– Terrestrial planets– Jovian
planets
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Earth in space• Differentiation: layering of terrestrial planets
based on chemical composition (i.e. density)– Crust: outermost
compositional layer• Thin, low-density
& rocky– Mantle: middle layer
• Rocky, intermediate density
– Core: innermost layer• High density &
metallic
Silicates
Mg; some silicates &
Fe/Ni mixed in
Solid Fe/Ni
Liquid Fe/Ni
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What makes Earth unique?• Atmosphere
– Rich in oxygen• Hydrosphere
– Water as solid, liquid &/or vapor
• Biosphere– Full of living
organisms• Regolith
– Blanket of loose debris covering Earth
– Soil
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What makes Earth unique?
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What makes Earth unique?• Plate tectonics
– Movement &interactions of large fragments of Earth’s lithosphere (plates)
– Distribution of volcanoes & earthquakes• Oceanic crust (basalt)
– Thinner, denser, younger– Basalt
• Continental crust (granite)– Older, thicker, less dense
• Uniformitarianism– Earth processes today operated
similarly throughout geologic history
– “the present is the key to the past”
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Why study geology?• Earth is our home• Depend on Earth for
resources• Limited resources
require management• Earth’s physical &
chemical processes affect us
• Need to appreciate our own role in geologic change
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Chapter 3:HOW OLD IS OLD?
The Rock Record &Deep Geologic Times
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Relative Age• Sequence of past geologic
events• Age of rock, fossils, or
other geologic feature relative to another feature
• Stratigraphy– Study of rock layers &
processes that form them• Strata
– Rock layers
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Relative Age• Principal of original horizontality: water-laid
sediments are deposited in horizontal layers
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Relative Age• Principle of stratigraphic superposition: each layer is
younger than the layer below it
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Relative Age• Principle of lateral continuity: sediments deposited in
continuous layers
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Relative Age• Principle of cross-
cutting relationship: layer must be older than any feature that cuts or disrupts it
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Gaps in the record• Numerical age
– Age of rock or geological feature in years before present
• Unconformity– Substantial gap
in rock sequence; shows absence of part of rock record
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Fossils and Correlation• Paleontology
– Study of fossils & record of ancient life on Earth– Use fossils to determine relative rock ages
• Principle of faunal & floral succession– Stratigraphic
ordering of fossil assemblages
• Correlation• Equate ages of
strata from 2 or more different places
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The Geologic Column • Geologic ti
me in 1 year
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Numerical Age & rates of decay• Radioactivity
– Process where element spontaneously transforms
– Radioactive decay• Parent atoms• Daughter atoms• Half life
– Time needed for 50% of parent atoms to decay into daughter atoms
• Radiometric dating– Use radioactive isotopes to
determine numerical age of minerals, rocks & fossils
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Rates of decay• Examine Figure 3.15 and determine the
relative age of rock layer 4
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The Age of Earth• Oldest rock: about 4
billion years old– Oldest mineral grain : 4.4
billion years old• Meteorites• Carbonaceous chondrites
– Thought to contain unaltered material from solar system formation
– Around 4.56 billion years old
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Lab Exercise 2: Maps
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Global Positioning System• Global navigation satellite system for
determining location on Earth’s surface– Need minimum of 3 satellites “visible” to
determine position on Earth’s surface
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Map Scale• Map Scale: relates map distance to Earth distance
– Verbal Scale: uses words for relationship• 1 inch equals 16 miles
– Graphic or Bar Scale: line or bar marked off in graduated distances• 0 is not at far left to allow for more precise measurements
– Fractional Scale: expressed as fraction or ratio• Example: 1/50,000 or 1:50,000
– 1 unit of measurement on map is equal to 50,000 units of same measurement on Earth» 1 foot = 50,000 feet or 1 cm = 50,000 cm
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Calculating Distance with Fractional Scales1. Measure distance on map to get “measured
distance” 2. Multiply measured distance by fractional scale
denominator to get “ground distance”3. Convert “ground distance” to other units• Example: If you have a map scale of 1:10,000 and a
measured distance of 3.5 inches; complete the following: _______ feet, _______ miles– How?1. 3.5 (10000) = 35000 inches 2. 35000 / 12 (1 foot) = 2916.67 feet3. 2916.67 / 5280 (feet in a mile) = 0.55 miles
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USGS Topographic Maps• Common scale = 1:24,000
– Called “7.5 minute” quadrangle map because map covers 7.5 minutes of both latitude & longitude
• Marginal map data gives important info:– Map title– Map location– Latitude & longitude– Map scales – Declination arrows
• True North (N or *) • Magnetic North (MN) • Grid North (GN)
– Map Symbols
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Contour Lines• Connect points of equal elevation• Contour line rules pg. 41 of your lab manual
– Steep slope – contour lines close together– Gentle slope – contour
lines farther apart– Contour interval – interval
of change between 2 contour lines
– Index contour – usually every 5th line is bolder & labeled with value• Helps to calculate
contour interval
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Contour Map Basics• Find the elevations of 2 index contours
– Subtract to find elevation change between 2index contours
• Count the number of lines you cross when going from 1 index contour to the other– Divide difference in elevation between
2 index contours by # of lines to find contour interval
• Example:– What is the contour interval on this
map? _____– What is the elevation of Point A? _____– What is the elevation of Point B? _____
A
B20 ft 780
ft725 ft
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Topographic Profiles
• Shown in “plan view” – Viewed from above
• Shows elevation change along a transect (A to B)
• Creates “side view” of the landscape
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Lab Exercise 1: Geolo
gic Time
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Index Fossils• Index fossil: short-lived species tied to
specific time period– ID’ing specific fossils can date rock layers to
specific time period– Can be used to point out missing
rock layers
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Tree Rings, Varves, & Coral• Tree rings
– Used to find tree age & ID conditions tree experienced in its lifetime• Count tree rings to find tree age• Wide rings = good conditions• Narrow rings = poor conditions
• Varves – Sediment layers that accumulate
annually due to seasonal fluctuations• Not frozen = sediment accumulation• Frozen = no sediment accumulation
• Coral– Correlation between # of daily growth increments & # of
days in year– Used to determine time period that coral grew