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

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

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

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

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

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

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

What makes Earth unique?

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”

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

Chapter 3:HOW OLD IS OLD?

The Rock Record &Deep Geologic Times

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

Relative Age• Principal of original horizontality: water-laid

sediments are deposited in horizontal layers

Relative Age• Principle of stratigraphic superposition: each layer is

younger than the layer below it

Relative Age• Principle of lateral continuity: sediments deposited in

continuous layers

Relative Age• Principle of cross-

cutting relationship: layer must be older than any feature that cuts or disrupts it

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

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

The Geologic Column • Geologic ti

me in 1 year

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

Rates of decay• Examine Figure 3.15 and determine the

relative age of rock layer 4

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

Lab Exercise 2: Maps

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

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

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

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

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

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

Topographic Profiles

• Shown in “plan view” – Viewed from above

• Shows elevation change along a transect (A to B)

• Creates “side view” of the landscape

Lab Exercise 1: Geolo

gic Time

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

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