Introduction to Landform Study

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Introduction to Landform Study
ART We have a profound artistic appreciation of
this landscape. Artistic interpretation portrays
this beauty in pictures.
MORE BEAUTY Understanding how this scene evolved
geomorphically adds to our appreciation and
pleasure of viewing a beautiful landscape!


SCIENCE Geomorphologic interpretation relies on
analyses and words rather than on artistic skills
to portray the results.
ART/BEAUTY SCIENCE/UNDERSTANDING MORE BEAUTY!
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Introduction to Landform Study

• Earth structure and composition
• Rock forming mineral families
• Rock types
• Important earthly concepts
• isostasy (for 9/18)
• driving and resisting forces (for 9/18)
• balance in landform evolution (for 9/18)
• thresholds in physical geography (for 9/18)

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Introduction to Landform Study

• Physical geographers, as they study the earth,
  are like
• A) Dermatologists
• B) Psychiatrists
• C) Neurologists
• D) Cardiologists

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Earth structure

• Earth a SOLID planet

1. Crust 2. Mantle 3. Outer core 4. Inner core
Q How do we KNOW whats down there?
Q Are we sure it is solid? Located at 84.4
degrees North and South Latitude are Polar
Openings that lead into the hollow interior of
our planet where the more at
www.ourhollowearth.com
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Earth structure

• How deep have humans traveled?
• Driefontein Mine, South Africa will be the
  world's deepest mine at 4.1km (2.5 mi) below the
  surface (UCCS to Patty Jewett G.C.)
• 441 million profit last year
• 15 mining-related deaths last year

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Earth structure

• How deep have humans drilled?
• The deepest well, at 7.5 mi (12 km), is located
  on Russias Kola Peninsula near Norway The Kola
  Well
• The US had Project Mohole in Oklahoma.

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Earth structure

• 1) Crust
• 5 km thick under oceans
• 25 km thick under continents
• lt 1 of earths volume
• Boundary between crust and mantle is called the
  Moho discontinuity or boundary

Red line indicates Moho discontinuity
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Earth structure

• 2) Mantle
• Extends to about 1800 miles
• Largest of the four shells
• Three layers in mantle
• Lithosphere (top portion of mantle crust) RIGID
• Asthenosphere SOFT
• Lower Mantle RIGID

The asthenosphere carries the lithosphere on its
back!
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Earth structure

• 3) Outer Core
• Extends from 1800 miles to 3100 miles
• Solid, very dense
• About 8000 deg. F.
• Radiates (up) convective currents of heat
• Iron, nickel
• Earths magnetic field generate here

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Earth structure

• 4) Inner Core
• Extends from 3100 miles to earth center
• Solid, very dense
• Iron/nickel
• About 10,000 deg. F.
• Iron, nickel, sulfur, carbon

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Earth composition

• Composed of minerals
• Solid, natural, inorganic, homogeneous
• Defined by their different elements and by their
  crystal structure
• carbon graphite diamond
• So far, about 4,400 minerals identified
• A few minerals are composed on only ONE element
• Only a few dozen are important constituents in
  Earths crust

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Earth composition

• Common minerals

• PYRITE FeS2
• OLIVINE (Mg,Fe)2SiO4
• PYROXENE (Mg,Fe)SiO3
• AMPHIBOLE (Ca2Mg5)Si8O22(OH)2
• FELDSPARS
• Albite NaAlSi3O8
• Orthoclase KAlSi3O8
• Anorthite CaAl2Si2O8
• KAOLINITE Al2Si2O5(OH)4

• QUARTZ (Silica) SiO2
• HEMATITE Fe2O3
• CALCITE CaCO3
• DOLOMITE CaMg(CO3)2
• GYPSUM CaSO4
• FLUORITE CaF2

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Earth composition
Notice how much silicon and oxygen there is in
crust composition? This makes the silicates happy.
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Earth composition

• 5 common rock forming mineral families
• 1. Silicates largest and most important family
• Contain oxygen (O) and silicon (Si)
• Hard and durable
• Feldspar (e.g., KAlSi308) and quartz (Si02) are
  two most abundant of the silicate minerals.

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Earth composition

• 5 common rock forming mineral families
• 2. Oxides an element combined with oxygen
• Most widespread oxides are those that are
  combined with iron
• hematite, magnetite, limonite

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Earth composition

• 5 common rock forming mineral families
• 3. Sulfides Sulfur and some other element
• For example, pyrite (FeS2), galena (lead),
  sphalerite (zinc), chalcopyrite (copper).
• Common mineral family

Galena, PbS
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Earth composition

• 5 common rock forming mineral families
• 4. Halides Least widespread
• salts (NaCl)
• 5. Native elements Discrete elements not
  combined chemically with other elements
• gold (Au) and silver (Ag)

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Earth composition

• Question What is regolith?
• Answer
• Question What is bedrock?
• Answer
• Question What is an outcrop?
• Answer
• Question What is a rock?
• Answer an aggregate of one or more minerals.

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The relationship between rocks and minerals
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Do you see the feldspar? quartz? horneblende?
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Earth composition

• Rocks fall into three main types depending on
  their origin and formative history
• Igneous rocks have solidified directly from a
  molten state, such as volcanic lava.
• Sedimentary rocks have been re-manufactured from
  previously existing rocks, usually from the
  products of chemical weathering or mechanical
  erosion, without melting.
• Metamorphic rocks result from processing, by heat
  and pressure (but not melting), of previously
  existing sedimentary, igneous, or metamorphic
  rock.

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Igneous rocks

• Examples of igneous rocks include
• basalt, gabbro, rhyolite, and granite
• (composed of feldspar, quartz, pyroxine, olivine)
• Igneous rocks are
• formed by the cooling and solidifying of molten
  rock
• from MAGMA (molten rock beneath surface)
• from LAVA (molten rock on surface)

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Igneous rocks

• The amount of silica (SiO2) is important
• LOTS of SILICA
• Magmas with a lot of silica form FELSIC igneous
  rocks
• FELSIC igneous rocks are light colored, such as
  quartz and feldspar
• NOT SO MUCH SILICA
• Magmas with not so much silica form MAFIC igneous
  rocks
• MAFIC igneous rocks are dark colored, such as
  olivine and pyroxene

feldspar
pyroxine
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Igneous rocks

• Crystal size
• Basalt and Rhyolite have small crystals because
  they are erupted by volcanoes and cool rapidly
  from the molten state.
• Gabbro and Granite have large crystals because
  they cool slowly from the molten state,
  underground.

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Igneous rocks

• Intrusive and extrusive
• Extrusive (volcanic) igneous rock
• basalt
• Columbia Plateau, most of ocean floor, northern
  AZ, HawaiI
• obsidian
• cooled rapidly
• others
• pumice, rhyolite, Andesite
• Intrusive (plutonic) igneous rock
• granite, diorite, gabbro
• some become exhumed by erosion (Pikes Peak)

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Igneous rocks
igneous extrusive
http//danny.oz.au/travel/iceland/p/3675c-basalt-c
olumns.jpg
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Igneous rocks
igneous extrusive
http//www.treknow.com/arizona/backroads/northeast
/images/MapAZ0338.jpg
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Igneous rocks
igneous extrusive
http//www.theeagleflight.org/old_site/photogaller
y/tx2id/Mogollon-Rim,-Arizona.jpg
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Igneous rocks
igneous extrusive
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Igneous rocks
igneous extrusive
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Igneous rocks
igneous intrusive (a batholith)
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Igneous rocks
igneous intrusive (a batholith)
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Sedimentary rocks

• Examples of sedimentary rocks include
• limestone, sandstone, shale
• Sedimentary rocks
• form as weathered material or sediment is
  transported by wind, water, gravity, ice
• sediment settles (is deposited) in an ocean or
  large body of water
• finally, cementation, and compaction from a heavy
  overburden converts the sediment into ROCK (a
  process called lithification)

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Sedimentary rocks

• Sedimentary rocks
• Clastic sedimentary rocks
• rocks composed of fragments of other rocks
• boulders, gravel, sand, silt, clay
• for example
• shale is composed of silt and clay
• sandstone is composed of, well, sand!
• Chemical / organic sedimentary rocks
• formed by accumulated soluble materials
• for example
• coal is composed of dead plants/animals
• limestone is composed of skeletal remains of
  coral and lime-secreting animals

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Sedimentary rocks
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Sedimentary rocks

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Sedimentary rocks
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Sedimentary rocks
http//home.earthlink.net/becky400/paleologia/xbe
d.jpg
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Sedimentary rocks
http//www-geo.phys.ualberta.ca/vkrav/Research/Lo
ess.htm
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Sedimentary rocks
http//www.grisda.org/colorado/index.htm
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Metamorphic rocks

• Examples of metamorphic rocks include
• marble, shale, gneiss, schist
• Metamorphic rocks
• have been changed by HIGH heat and pressure
• they have been COOKED
• limestone COOKED is marble
• sandstone COOKED is quartzite
• shale COOKED is slate

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Metamorphic rocks
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Metamorphic rocks

• Metamorphic rocks
• Platy (flattish) minerals such as clays or
  micas tend to align themselves parallel to each
  other when under pressure. 
• If the minerals are aligned in metamorphic rocks,
  the rock is said to be FOLIATED

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Metamorphic rocks
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Metamorphic rocks
http//www.ghosttowngallery.com/ghostsco/marble110
9-085.jpg
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Metamorphic rocks
slate
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The rock cycle
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RED igneous BLUE metamorphic YELLOW
sedimentary