GEO.3425 - FINAL

Aeolian

• wind action and wind processes

• movement and erosion of particles by wind

• erosion, transportation, and deposition of materials

Modes of Transport by Wind

1. Suspension

2. Saltation

3. Surface Creep

Suspension

fine particles suspended in the air

Saltation

bouncing and skipping of slightly larger particles

impact: when grains hit other grains and knock them into the air

Surface Creep

grain size to large for saltation; pushed forward by saltating particles

Major Types of Aeolian Erosional Processes

1. Deflation

2. Abrasion

Deflation

• wind erodes/removes loose fine grained material

• transported away, heavier materials remain

Abrasion

• when two materials are rubbed together and slowly abrade/grind away at each other

• sandpaper effect performed by the wind

• often restricted to the area immediately above the ground

Desert Pavement

• type of deflation

• larger deposits remain and create an armored surface of coarser grained sediments across a windy surface

Ventifacts

• artifacts of the wind

• pitted, grooved, polished

Yardangs

large-scale, wind-sculpted rocks

Types of Deserts

1. Subtropical Deserts

2. Rain Shadow Desert

3. Continental Desert

4. Polar Desert

5. Coastal Desert

Subtropical Desert

Sahara Desert

Rain Shadow Desert

Death Valley

Continental Desert

Gobi Desert

Polar Desert

Antarctica

Coastal Desert

Namib Desert

Four Major U.S. Deserts

1. Mojave

2. Great Basin

3. Sonoran

4. Chihuahaun

Wind

• horizontal movement of air across Earth’s surface

• produced by differences in pressure between one location and another

• two main properties: speed and direction

Santa Ana Winds

• develop in Southern California when there is high pressure over the Great Basin

• air is warmed and dried as it moves and creates significant fire danger

Chinook Winds

• air descends a mountain barrier and its relatively humidity lower the air compresses and warms

• produces relatively warm, dry conditions

Katabatic Winds

• larger, regional winds

• gravity drainage winds

• thermal high pressure (cold, dense air) flows downslope from elevated plateaus or highlands

• ice sheet winds

Ripples

• smallest aeolian landform

• small ridges of sand that form throughs and crests

Morphology of Sand Dunes

3 General Shapes of Dunes

1. Crescentic Dunes

2. Linear Dunes

3. Star-shaped Dunes

Types of Dunes

1. Barchan

2. Parabolic

3. Longitudinal

4. Transverse

5. Barchanoid

6. Star-Shaped

Barchan

crescentic dunes with the horns of the dunes pointed downwind

Parabolic

crescentic dunes with the horns pointed upwind

horns typically anchored by vegetation

Longitudinal

• linear, ridge shaped dune

• aligned parallel with the wind direction

Transverse

• long, slightly sinuous w/ asymmetrical ridge

• only one slip face

• aligned perpendicular to wind direction

Barchanoid

• wavy, asymmetrical

• formed from coalesced barchans w/ ridges aligned perpendicular to effective winds

Star-Shaped

• formed in areas w/ no dominant wind direction

• lower winds just the arms migrate; higher winds the center stars migrate

Desertification

• the degradation of land in arid, semi-arid, and dry sub-humid areas

• driven by human activities (such as overgrazing, deforestation, and poor agricultural practices) and climate variations

• results in the loss of vegetative cover and biological productivity

Karst Definition

terrain in which soluble rocks are altered above and below ground

Lithology of Karst Rocks

• develops primarily on limestone (also forms in dolomite (slowly) and evaporites (halite and gypsum))

• greater and % of calcite, the more karst develops

Porosity and Permeability of Karst

needs high porosity and high permeability

Chemical Reactions forming in Karst

Limestone (Calcite Dissolution)

H₂CO₃ + CaCO₃ → Ca⁺² + 2HCO₃-

Conditions for Karst Formation

1. formations must have 60% or more calcium carbonate

2. Complexly jointed bedrock

3. Aerated zone between the ground surface and the water table

4. vegetation to supply organic acids that help dissolve the limestone

Karst Landforms

1. Sinkholes

2. Cockpit and Tower Karst

3. Stalactites + Stalagmites

4. Uvalas

5. Disappearing Stream: Sink vs. Spring

Collapse Sinkholes

• sinkholes that form from the bottom up

• groundwater dissolves bedrock underground until the surface collapses

• not visible on the surface until they collapse

Solution Sinkholes

• form from the top down

• solution process create a depression that slowly deepens

Cockpit + Tower Karst

• only occurs in the wet tropics where thick limestone beds are weathered into towers and gorges

• can be over 600 feet high

Stalactites

attached to the ceiling

Stalagmites

attached to the floor

Uvalas

Disappearing Stream

Sink vs. Spring

Current Ice Age

Quaternary Ice Age

Holocene Epoch and Quaternary Period

Distribution of Ice in the World

• Covers ~10% of Earth’s Surface

• Antarctica, Greenland

Definition of Glaciers

large, non-stationary masses of ice formed by accumulation of snow into ice

Three Stages of Forming Glacial Ice

1. snow survives the summer

2. following winter to old snow is compressed and recrystallized into firn

3. dense glacial ice is formed as firn and snow are compressed and re-crystallized into a dense glacial ice

Firn

intermediate stage between snow and glacial ice

compact and granular texture

Two General Types of Glaciers

1. Alpine or mountain glaciers

2. Continental glaciers

Alpine Glaciers

• glacier in a mountain range

• four subtypes

  • 1. Cirque

  • 2. Valley

  • 3. Piedmonth

  • 4. Tidewater

Continental Glaciers

• attached to land

• “Ice sheets”

Ice Sheets

mass of glacier that covers more than 50,000km

Ice Cap

circular and covers area of less than 50,000km

Ice Field

elongated pattern usually less area than that of an ice cap

Cirque Glaciers

glacier in a bowl-shaped recess at the head of a valley

Valley Glaciers

in steeped wall valleys

Piedmont Glaciers

spread out as wide lobe as it leaves a narrow mountain valley to enter a wider valley or a plain

Tidewater Glaciers

glacier ends in a body of water influenced by tides

Two Ice Sheets in the World

Mass Balance

relationship between accumulation and ablation of snow and ice

Accumulation

Ablation

Equilibrium Line Altitude

Movement of Glaciers

1. Internal Flow

2. Extending and Compressive Flow

3. Basal Sliding

Internal Flow

increasing flow rate from bed to surface

Extending and Compressive Flow

• velocity increases in extension zones

• velocity decreases in compressive zones

Basal Sliding

process that occurs at contact between underlying glacial rock bed and glacier base

Regelation

process by which ice melts under pressure and then refreezes when the pressure is released; occurs mainly at the base of a glacier

• pressure melting on the upslope side

• refreezing on the downslope side

Glacial Features

• Bergschrund

• Crevasse

Bergschrund

Crevasse

deep v-shaped cleft formed in the upper brittle part of a glacier as a result of the fracture of ice undergoing extension

Glacial Landforms

1. Striations

2. U-shaped Valley

3. Roche Moutonnee

4. Erratics

5. Cirque

6. Arete

Tarn

small mountain lake where glacial cirque melted

Striations

U-Shaped Valley

glacier throughs give the valleys a more broadened wider base

Roche Moutonnee

rocky hillock w/ gently inclined smooth up-valley facing slope resulting from glacial abrasion and a steep rough down valley facing slope resulting from glacial plucking

Erratics

Cirque

armchair-shaped hollow w/ steep sides and back wall formed as result of glacial erosion on a mountain side

Arete

“knife edge” sharp, narrow, pinnacled ridge, formed as a result of glacial erosion from both sides

Glacial Depositional Landforms

1. Glacial Drift

2. Moraines

3. Esker

4. Kame Dumlin

Glacial Drift

general term for all glacial deposits both sorted and unsorted

Till

ice deposits that are unstratified and unsorted

Stratified Drift

sediments deposited by glacial meltwater which are sorted by size

Moraines

1. lateral

2. Medial

3. Terminal

Lateral Moraine

forms along each side of a glacier

Medial Moraines

two glaciers with lateral moraines join

Terminal Moraines

eroded debris dropped at the glacier’s farthest extent

Esker

sinuously curving, narrow ridge of coarse sand and gravel, forms along channel of melt-water stream under glacier

Kame

hill deposited directly by water, often in crevasse

Drumlin

elongated hill in the shape of an inverted spoon formed by glacial ice acting on underlying unconsolidated till or ground moraine

Periglacial

cold-climate processes, landforms, and topographic features that exist in cold NON-GLACIAL conditions regardless of their proximity to glaciers

Location of Periglacial

• occupy more than 20% of Earth’s Land surface

• in subarctic and polar climates

• at high latitude or high altitude in lower-altitude mountains

Permafrost

occurs when soil or rock remains below freezing for at least two consecutive winters and the intervening summer

Continuous Permafrost

-7°C

Discontinuous Permafrost

-1°C

Active Layer

zone of seasonally frozen/thawing ground that exists between subsurface permafrost layer and the ground surface

thickness increased with decreasing latitude

Talik

unfrozen ground that may occur above, below, or within body of discontinuous permafrost or beneath a water body in the continuous zone