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LSU / Geography / GEOG 2051 / What are the three main types of topography?

What are the three main types of topography?

What are the three main types of topography?


GEOG 2051

What are the three main types of topography?

Thursday 1.10.19

Physical Geography

4 spheres (subdivisions) of physical geography: lithosphere (solid parts of the globe), hydrosphere (water portions), atmosphere (earth’s air; where weather occurs), biosphere (earth’s living things)

Geographic Studies:

Geomorphology - focuses on the lithosphere

Hydrology - focused on water issues

Climatology - studies the atmosphere

Biogeography - study spacial arrangement of living organisms

*this course will mostly focus on the lithosphere, but we will also study human impact The spheres are all interconnected & they influence each other

GEOG 2051

Tuesday 1.15.19

What are the different chemical processes?

Methods and Tools

Scientific Method 

**method to create new knowledge

1. draws on pre-existing knowledge/our image of the real world (the sum total of everything you’ve learned in your entire life)

2. a gap in knowledge/a question/a problem

3. develop a hypothesis (provisional explanation of some phenomena that needs to be verified...an educated guess)

a. hypothesis vs. theory

i. hypothesis - educated guess, either not tested much or not tested yet at all

ii. theory - well-accepted answer, well-tested, and supported by many experiments

4. testing/evaluation (experiments, data collection, analysis) If you want to learn more check out Why does heart failure cause pink sputum?

a. cannot prove truth...you can only disprove!!!!

What are the four physical processes?

b. either accept or reject the hypothesis (if rejecting it, come up with a new hypothesis)

**theory - always try to be a bit skeptical (everything is subject to being revised...all of our theory is just an approximation of our best knowledge at the time) *you’re actually trying to demonstrate that your hypothesis is incorrect (falsifying the hypothesis)

Systems Theory 

*group of very abstract concepts and ideas...their abstract nature is what gives them power

1. starts out with the idea of a system

a. defines what a system is (a set of objects and their attributes that are linked together by flows of matter and energy)

b. two types of systems

i. open - allows exchanges of energy & matter with the surrounding environment ← systems must be open to last over time

ii. closed - no exchange of matter & energy with the surrounding environment

2. budgets/balances of matter & energy

a. energy & mass cannot be created or destroyed...what goes into a system must either come out of it or add to what is in storage

b. inputs → add to what is in storage

outputs → take away from what is in storage

i. POSITIVE BUDGET: inputs are larger than outputs (amount in storage will increase) We also discuss several other topics like How to read polls?

ii. NEGATIVE BUDGET: inputs are smaller than outputs (amount in storage will decrease)

iii. BALANCED BUDGET: inputs equal outputs (storage remains constant over time) ← EQUILIBRIUM (natural systems must have equilibrium to persist)

*static equilibrium - stationary, no change

*dynamic equilibrium - constant change, but averages out to where there is a balance (most systems we will study will have a dynamic equilibrium)


Island ecosystem Don't forget about the age old question of How has the process by which young adults find intimate partners changed?

Biomass - amount of living material in storage on the island

grass/plants ← island mice ← island wolf

With an increase of rainfall (input → water), there will be an increase in grass, leading to an increase in mice, leading to an increase in wolves (biomass increase)

When there is a dry period, there will be less grass, less mice, and fewer wolves (biomass decrease)

Lag time - time between some change in inputs (or environmental conditions) and the system’s response to that change

Ex: time it takes to flood after an increase in rainfall is that system’s lag time Ex 2: time it took for the island mice population to start decreasing after the grass on the island went away (and the time it takes the wolf population to die off)


*system response to some change in inputs (or environmental conditions) that acts to influence the initial change

1. POSITIVE FEEDBACK: original change is enhanced (tend to be destructive for systems)

a. Ex: ducks continue to grow and reproduce until the world is full of ducks 2. NEGATIVE FEEDBACK: original change is reduced (tend to be constructive for systems)

a. Ex: the more ducks there are, the less food there is, the more competition there is for good nesting spots, and the more predators there will be *Carrying capacity - the number of organisms an ecosystem can support (will change over time, as it depends on factors like food and water availability) ← adjusts according to the changing environmental conditions We also discuss several other topics like What is medical ethics?

GEOG 2051


Physical Geography

Observation Platforms 

1. Airplanes (one of the most important platforms of the last century)

2. Satellites began to emerge at the beginning of the 19th century and rapidly took over as the primary method of remote sensing

a. Geostationary orbit: continuous view of the same orbit (rotates at the same speed as the earth)

b. Polar orbit: satellite constantly moving over a new location (moves from pole to pole...N to S) tend to be closer to the earth - cover a smaller area, but provide a better resolution

3. Geographic information systems (GIS) has easily become the most important tool in geography today

a. It’s essentially a digital map

b. GIS relies on layered data to customize maps & speed up the process of mapping data and information

Nature of the Earth: History, Internal Structure, Materials 

Earth’s History

1. Nebular Hypothesis

a. nebula → sun, planets, etc. → 4.6 billion years BP

2. Geologic Time Scale

a. Precambrian - beginning of the earth until about ½ billion years ago Don't forget about the age old question of Huntington disease affects what parts of the brain?

b. Phanerozoic - current time period

c. Quaternary is ~the last 2 million years

3. Relative and Absolute Dating

a. Superposition - oldest rocks will be at the bottom of a formation, and the youngest rocks will be at the top (RELATIVE)

b. Dendrochronology - with every growing season, trees add another layer (check the rings to see the age)...the rings are also indicative of how good the growing season was

c. Radiometric dating (ABSOLUTE)...ex: carbon 14 dating

i. Parent isotope (carbon 14 is an unstable parent isotope - it breaks down over time, which is useful for carbon dating because it occurs at a We also discuss several other topics like What is the teleological argument simple?

constant fixed rate)

ii. Daughter isotope...half life

1. Carbon 14 has a half life of ~5,000 years, and it breaks down into

nitrogen 14, which is the daughter material

2. 1 half life...50% parent 50% daughter; 2 half lives...25% parent

75% daughter; 3 half lives...12.5% parent 87.5% daughter

4. Catastrophism or Uniformitarianism

a. Catastrophism - linked to biblical origins; earth was shaped by a catastrophe b. Uniformitarianism - the scientific explanation of the world’s creation; came about in the late 1600s/early 1700s; “the present is the key to the past”

5. Bretz

a. Earth scientist working in the early 1900s

b. Mapping the channeled scablands in eastern washington state...discovered lower monumental dam ripples

Earth’s Interior Structure

1. Earth is divided into 3 major layers (each layer has subdivisions)

a. Core - very center of the earth (very dense material...density of ~13 grams/cubic centimeter...on the surface, it’s ~8 grams/cubic centimeter)

i. Inner core - made up of primarily solid metal (iron, nickel, etc.)

ii. Outer core - made up of primarily liquid molten metal (iron, etc.)

b. Mantle - largest layer of the earth in terms of volume (~80% of earth’s material) i. Asthenosphere - partially molten/plastic

ii. Uppermost mantle (outermost layer) - solid w/ a lower density...basically floating in the asthenosphere

c. Crust

i. Oceanic

ii. Continental - tends to be less dense than the oceanic crust material *crust + uppermost mantle = lithosphere 

2. Density tends to be higher toward the center of the earth, and the temperature gets hotter

Earth’s Materials

**About 100 naturally occurring elements, which are the basic building blocks of all matter 1. Common elements

a. Oxygen (~½ of the crust)

b. Silicon (~¼ of the crust)

2. Minerals - inorganic crystalline material, formed by combining elements a. Oxygen + silicon + iron + potassium + magnesium + mineral called Mica 3. Rocks are formed by combining minerals

a. Mica + Quartz + Feldspar = rock called Granite

4. The Rock Cycle - 3 categories of rocks

a. Igneous - formed when magma cools and solidifies

i. Weathering causes sediment

b. Sedimentary - formed through lithification

c. Metamorphic - formed through metamorphism (exposure to heat/pressure) 1.24.19


1. Sedimentary (3 major types)

a. clastic sedimentary rocks - formed through lithification

i. Classified by the size of the particles that make up the rock (sand

between 2 & .06mm; silt between .06mm & .001mm; clay anything

smaller than .001mm)

b. chemical sedimentary rocks - tiniest possible particles you can get; formed through a few different processes (evaporation, precipitation)

c. organic sedimentary rocks - biological sedimentary rocks; originally comes from living organisms (best examples are coal and limestone)

2. Igneous rocks - formed from cooling magma

a. plutons - formed of intrusive igneous rock

3. Metamorphic rocks - have been altered at the molecular level by long term exposure to enormous heat and/or pressure

Major Processes 

1. Isostasy - large scale vertical movements of the earth’s crust


GEOG 2051

Physical Geography

Plate Tectonics 

1. The world’s outermost skin isn’t a continuous open layer - they’re broken into large chunks called lithospheric plate

2. Divergent Boundaries - plate boundaries where the two plates are spreading apart (there’s too much heat rising upwards, it spreads out and causes convection currents to develop in the asthenosphere) -- where we form new crust material

a. Seafloor spreading zones

b. Rift valley - phenomena created when divergent boundaries form in a land zone 3. Convergent Boundaries - plate boundaries where the two plates are slamming into each other (usually, the denser plate will be forced back down into the mantle/the asthenosphere) -- where we recycle old crust material

a. Subduction zones

4. Transform Boundaries - two plates are trying to slip past each other side by side in opposite directions

Wilson Cycle 

1. A continent rifts when it breaks up

2. As spreading continues, an ocean opens; passive margin cools and sediments accumulate

3. Convergence begins; an oceanic plate subducts, creating a volcanic chain at an active margin

4. Terrane accretion from the sedimentary wedge welds material to the continent 5. As two continents collide, mountains form

6. The continent erodes, thinning the crust

Global Supercontinent Cycle 

1. Continents united in one big supercontinent; over time, rift valleys begin to form and then subside

2. It starts to flood eventually, leading to the development of our three ocean basins 3. After about 350 million years, subduction zones start to chew up our ocean basins, bringing continental fragments back together

4. Eventually, the continental fragments will slam into one another, forming the next global supercontinent

Pangaea - “all earth” - about 135 million years ago, the continents were all still attached to each other; about 65 million years ago they were starting to spread apart, but they were still pretty connected

Energy Source

*only two energy sources on earth: the sun, and internal heat

*plate tectonics powered by internal heat from the core


Wegener’s Drift

*Alfred Wegener found a lot of evidence suggesting Pangaea existed (fossils in different areas, the discovery of geological formations that extended to multiple continents [atlas mountains]) Wegener’s theory was originally referred to as the theory of continental drift; during WWII people started trying to map the sea floors, and they found a mountain range running down the middle of each of the ocean basins (mid-ocean ridges)

Paleomagnetism, a new theory, started to emerge - the study of old magnetic fields *our magnetic field does not stay fixed in place; every few years or so it reverses itself People discovered that the magnetic fields of rocks were arranged in reverse polarity, which indicated that they were formed in different time periods

Radiometric dating - rocks along the mid-ocean ridges were very very young; toward the continents, the rocks would consistently get older and older, which indicates a growth sequence

Major Processes: Folding, Faulting Orogenesis 

*typically occurs along plate boundaries

Folding & Faulting

*Folding occurs when the pressure does not crack the rock, just bends it

*Faulting can occur anywhere that there is a break or crack in a rock (a joint); a fault is a particular type of joint (where the rock fractures under pressure)

a. Tension force (pulling away) ← → which typically leads to stretching

b. Compression force (squeezing in) → ← which leads to bending into a fold c. Shear force (two forces acting in opposite directions, offset from each other) - leads to horizontal shifting/bending


*anticline/syncline - each made up of two folds

*symmetrical fold - where the dips are symmetrical to each other

*asymmetrical fold - where the dips differ from one another

*dip & strike - dip refers to the angle of the fold, strike refers to the ridge crest line *plunge of the fold - refers to the angle that the ridge crest line makes with respect to the horizontal surface

Faults - different faults created depending on the type of force

*tension - leads to a normal fault

*compression - leads to a reverse (thrusts) fault

*shear force - leads to strike-slip (lateral, transform) fault

Orogenesis (mountain formation)

*occurs primarily along convergent plate boundaries

Convergent boundaries

1. oceanic - oceanic

a. subduction...volcanic activity (how Japan was formed)

b. volcanic island arc mountain systems

2. continental - oceanic

a. subduction...volcanic activity & build up of mechanical forces along mountain systems (ex: Andes Mountains)

3. continental - continental

a. mechanical/compressional forces (Himalayas)

Major Processes: Earthquakes and Volcanism 


*earthquake activity commonly takes place in association with plate boundaries (but can occasionally happen away from them); earthquakes act as a line to delineate between the plate boundaries

What causes earthquakes?

Elastic rebound theory explains this - it is based on the notion of a rubber band. When you stretch a rubber band, you’re storing energy - if you store too much, it breaks (and the energy is released). Wherever we have a fault, we can potentially have an earthquake. **Asperities are places where blocks of rock are stuck together in place. Energy is released and travels through the ground in the form of seismic waves when energy at asperities exceeds the strength and it is released.

Earthquakes typically occur in groups. Asperities will break and give way, and one will trigger another and so on and so on.

*foreshocks - precede an earthquake

*aftershocks - follow an earthquake

Epicenter - the point on the surface directly above the asperity

Focus - directly below the epicenter; point below ground where the asperity gives way

GEOG 2051


Physical Geography

Exogenic processes - driven by solar power

Endogenic processes - driven by earth’s internal heat

● Craton - an area of very old rock on each one of the continents (rocks 1-4 billion years old); basement rock is where the craton is very deeply buried; shield is where the craton is exposed/close to the surface

○ Accreted terranes - area along the outskirts of cratons (terrane = area of foreign land)

○ Topography (terrain) - refers to the overall shape of the land

○ Relief - the difference in elevation between the highest and lowest points in an area

Topographic regions 

● mountain ranges (areas with relief of 2,000 feet or more) → convergent plate boundaries ● hills and low tablelands (areas that have relief between 200 and 2,000 feet) ● plains (areas with relief that is less than 200 feet

Order Features

● 1st order features

○ cover huge vast areas (continents and ocean basins)

○ takes millions of years for changes to occur (huge time scale)

○ endogenic processes

● 2nd order features

○ cover very large area (mountains)

○ very large time scale

○ endogenic processes

● 3rd order

○ large area (specific/smaller mountain range)

○ large time scale

○ exogenic processes start to become a specific component in the landscape’s development

● 4th order

○ covers pretty big area

○ shorter time scale

○ exogenic processes

● 5th order

○ Rivers

○ Exogenic

○ small spatial scale

● 6th order

○ smaller spatial scale

○ exclusively exogenic at this point

● 7th order

○ ripples and tiny features

○ super short time scale and tiny spatial scale

Weathering, Slopes, & Mass Movements (Exogenic Processes)


● the breakdown of earth’s materials into smaller components

○ physical weathering - mechanical processes

○ chemical weathering - attack at the molecular scale

● parent material - bedrock

○ regolith (broken up parent material)

■ soil - mix of remains of parent material and other organic material

(affected by other things interacting with the ecosystem)


● rock characteristics

○ jointing (cracks in rocks)

○ hardness of the material

● climate

○ temperature and precipitation are important in determining the kinds of weathering processes that will occur

■ warm & wet areas → chemical weathering

■ Cool & dry areas → physical weathering

● hydrology (movement of water through the environment)

○ determines the amount of exposure surface materials will have to water ● topography

○ Can generate orographic precipitation (precipitation - rain or snow - that is being caused by mountains)

○ creates microclimates (climate will be different from the rest of the area) ● biological factors

Physical Processes

● freeze-thaw/frost action

○ when water freezes, it increases in volume

● root wedging

○ roots break concrete

● crystallization

○ often confused as a chemical weathering process...but it’s PHYSICAL WEATHERING

○ freeze-thaw is a type of crystallization

○ mainly present near beaches & salt water

● exfoliation/pressure-release/spalling

○ layers flake off/peel off of rocks

○ pressure causes rock to inflate and expand, which leads to it shedding layers Chemical Processes

● oxidation

○ rusting

○ oxygen atoms from water get bonded to iron atoms in rocks to create an oxide, which leads to rust

○ a lot of rust near places with a lot of rain/water

● hydrolysis

○ attacks granite

○ strips atoms away from the feldspar minerals, leaving behind the other minerals present in granite (mostly quartz left over)

● carbonation

○ process that dissolves minerals

○ very effective at attacking limestone, a common bedrock

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