Geology 1104 Final Laura Mallard

Icefall

-An ice sheet that spills over a cliff, forming a steeply flowing mass of ice called and icefall

Lake Missoula and the Channeled Scablands

-Called scablands because it was crossed by so many gorges. It didn't make sense because the area did not contains streams or rivers large enough to have carved gorges. J Harlan Bretz proposed a hypothesis that on more than occasion glacial Lake Missoula breached the glacial dam holding back its waters and catastrophic torrents of water raced across the landscape to the west,carving into the scablands. With this came the movement of the boulders, carved smooth depressions(pot holes) into the bed rock and formed enormous ripples. The ripples record the movement.

Piedmont Glaciers

-Glaciers or ice sheets that flow out of the mountains into broader, less confines topography and spread out.

Parts of a wave

-Height -Trough -Crest -Wavelength -Wave Base

Where do glaciers form?

-High peaks of the andes, patagonia -Antarctica -Highest parts of tibetan plateau and the Himalaya -In islands and peninsulas in Asia that are along the arctic ocean -Greenland -Alaska -Northern Canada -Rocky Mountains -Coast range of British columbia -Larger volcanoes and other high peaks of the cascade range

Causes of Crevasse

-Internal stress from the glacier moving -Happens more frequently when a glacier moves around a curve or where the land beneath the glacier changes slope- either from a steep slope to a more gentle slope of a gentle slope to a steeper drop

Ice Sheets

-Largest accumulations of ice -Covering nearly all of Antartica and Greenland

Abrasion

-Rocks and smaller size sediment, at the glaciers base scrapes at underlying bedrock through a process called abrasion.

Characteristics of Glaciers

-Snow and Ice accumulating faster than they melt -Higher elevations -Higher Latitudes -Distinctly Blue -Grooves, ridges, and sediment rich streaks

How do snow and Ice accumulate in glaciers

-Snow falls as individual flakes, they then get pressed together by the weight of the other snowflakes -As more snow accumulates on top, snowflakes farther down are compressed forcing out more than 50% of the air. Become compressed into small irregular spheres of more dense snow -With increasing depth and pressure, the snow begins to recrystallize into small interlocking crystals, forming solid ice. Ice is crystalline which makes it a rock.

Different ways to determine where and when the most recent ice age occured

-When there were heavier isotopes in the sea that meant there was a time of glaciation -When there were light isotopes in the sea, that meant it was a time of melting. -Looking at if there were more heavy O2 isotopes in marine shells(O2 -18) or if there were lighter O2 isotopes in the marine shells(O2-16) - Also digging large ice chunks out of greenland and other places that are cold

Valley glaciers/Alpine glaciers

-glaciers that flow down valleys -fairly narrow such as several kilometers wide but can flow down valleys for tens of kilometers

Zone of accumulation

-upper part of glacier or ice sheet, where snow and ice are added faster than they melt. Gravity then causes it to move downhill.

How long was the Ice Age

2 Million Years

How much of Greenland is covered in ice?

80%

How much of antarctica is covered in ice?

98%

Fjord

A U-Shaped valley eroded below sea level and subsequently flooded by a ride in sea level

Cirque

A bowl shaped basin carved by a glacier (erosional)

Crevasse

A deep crack or fissure in the ice of a glacier.

Tarn

A lake within a glacially scoured depression in a cirque

Lake Lahontan

A large ancestral lake filled with low basins of western Nevada. Was up to 240M deep about 13,000 years ago and some modern lakes in the area are remnants of this larger ice-age lake.

Col

A low point on the arete can afford a pathway from one side of the ridge to the other side and is refered to as a col.

Marine Terrace

A platform can be uplifted above sea level, at which point we call it a marine terrace

Calving

A process that occurs when the ice tends to spread or be pulled apart, forming large crevasses within the ice which allows for large blocks of ice to collapse ff the front of the glacier, which is called calving

Milutin Milankovitch

A serbian astronomer and geophysicist who recognized that Earth's climate could be influenced by the changes in Earth's tilt and orbit shape.

Paternoster Lakes

A series of tarns that are connected by a stream

Drumlin

A streamlined hill that is composed of toll and glaciofluvial deposits. Forms as a moving glacier sculpts these soft materials into a shape designed to minimize drag, similar to the shape of a shark or a porpoise.

Interglacial Period

A time during an ice age when glaciers were melting and retreating

Glacial Period/Glacial Maximum

A time when glaciers were most widespread

Loess

Accumulations of windblown silt, which is usually glacially derived.

Spit

Along some coasts a low ridge of sand and other seiment extends like a prong off a corner of the coast. Such a feature is a sand spit or a spit and is easily eroded, especially by storm waves.

Lake Missoula

An ice age lake filled low, interconnected basins in the Rocky Mountains of Western Montana. It caused catastrophic flooding. Shorelines from this lake were etched as horizontal lines into the hills surrounding Missoula, Montana.

Dropstones

An unusual feature of some marine and lake sediment is the presence of scattered stones in an otherwise fine-grained, clastic sediment. They have been carried within floating icebergs and then dropped into fine sediment on the seafloor or lake bottom.

Tillite

Ancient examples of past glaciations which lithified till into rock and consolidated it, making it tillite

Glacial Drift

Any sediment carried by ice, icebergs, or meltwater

Driftless areas

Areas where there is rougher topography due to never being glaciated

Roche Moutonnee

Asymmetric feature created by the combination of plucking and abrasion. Plucking creates a steeper side to the feature while abrasion creates a gentler slope

Icebergs

Blocks of ice that fall into the water and float.

Subglacially

Carried at the base of the ice of the glacier

Supraglacially

Carried at the surface of the glacier

Englacially

Carried within the ice of the glacier

Plucking

Concentrated on the downflow side of irregularities in the underlying bedrock, but can occur anywhere beneath a glacier. Occurs where rocks become loosened by and incorporated into ice at the base of a glacier. Also liberates large rocks that are left behind when the glacier melts,

Wave-Cut Platforms

Continued erosion at sea level can bevel off bedrock, forming a flat wave cut platform. May be covered in water are high tide but fully exposed at low tide.

Why is Crystalline Blue?

Crystalline ice contains less air and commonly has a bluish color due to the way oxygen-hydrogen bonds interact with light.

Glaciofluvial deposition

Deposition of sediment by glacial streams, refers to the involvement of glaciers and streams

Drumlin Fields

Drumlins that form in groups or fields, most common in Eastern Wisconsin and central New York. Only glacial feature on the page formed by advancing ice. The rest are forming by stagnant ice or retreating ice.

Melting Ice and Sea Levels

Due to the melting Ice, sea levels rose by carving new river valleys and flowed into the sea

Pinnacles and Sea Stacks

Erosion along a shoreline is not uniform and some areas of rock are left behind as erosion cut back the shoreline. Such remnants can form pinnacles and isolated steep sided knobs called sea stacks, like these along Australia's famous Great Ocean Road.

Caves and Sea Arches

Erosion concentrate in the tidal zone where waves can undercut cliffs-forming caves. Erosion can cut through small promontories jutting out into the sea, forming arches or windows through the bed rock. Most common among uplifted coasts.

Kames

Form where meltwater in stagnant ice deposited sediment in ice crevasses or in the space between the glacier and the land surface, form fairly round hills.

Terminal Moraine

Forms at the terminus, end, of a glacier and marks the glacier's farthest downhill extent

Frozen solid Glaciers and their movement

Frozen glaciers that are completely frozen at the base can get locked onto the bedrock, especially if the underlying bedrock is extremely irregular and is relatively dry.

Glacial erosion and valleys

Glaciers typically change V shaped valleys into a glacially carve U shape valley- San Juan Mountains of Colorado

Arete

Hard bedrock ridges that flank cirques are commonly narrow, sharp, and jagged, like the ridges shown below

Ice Shelf

Ice sheets and glaciers that flow into the seas with such large quantities that they form a large ice shelf that floats on the seawater

Kettle Lake

If a kettle is intersecting the water table it will fill with water becoming a kettle lake

Not frozen solid glaciers and their movement

If the bedrock-glacier is less irregular or contains water from melting ice it will usually be able to slide over the bedrock- move relatively rapidly.

Permafrost

In cold regions, below some depth, water in and below the soil remains frozen year after year

Snowfields

Large accumulations of snow and ice that never move

Continental Ice Sheets

Large glaciers the cover parts of continents

Sea Ice

Large masses of ice that form on the surface of a lake or the sea when they freeze. Called this specifically in the ocean.

Glacial Erratic

Large rocks left by the glaciers that are typically compositionally different from the local bedrock, so they seem out of place. Boulder like.

Glacier

Mass of flowing Ice

Englacial Transport

Material encased within the ice. Retains the debris somewhere within the glacier or internal shearing, along the inclined flows planes shown here, can bring englacial debris to the surface of the glacier where it becomes supraglacial debris.

Glacial Outwash Plain

Melting ice sheets produce large braided streams that carry glaciofluvial sediment away from recessional or terminal moraines and deposit it either nearby or some distance away. Can be pitted by kettle that from depressions or ponds.

Glaciofluvial Outwash

Meltwater in the foreground is issuing from the glacier in the background and carries abundant sediment

Spring Tide

Occurs when the side of the moon is either fully illuminated or not at all and the sun is also pulling with the same amount of force

Barrier Islands

Offshore of many shorelines are low islands that act as barriers, partially protecting the coast from large waves and rough seas. Many barrier islands are barely above sea level and consist of loose sand, including sand dunes, and salt water marshes

Sandbar

Offshore of many shorelines is a low sandy area called a sandbar. typically submerged much of the time and can shift positions as waves and long shore currents pick up, move and deposit the sand.

Three ways Glaciers cause erosion

Plucking, abrasion, from glacial meltwater

Thick Glaciers

Produced by being confined within valleys as they flow from higher elevations to lower elevations. As adjacent ice filled valleys merge, so do the glaciers, producing commonly thicker masses of flowing ice

Terminal Moraines

Represents the maximum forward extent of the front of the glacier. Has the same shape and character as a recessional moraine but it is farthest in front.

Outwash Plains

River and streams deposit sediment on broad outwash plains in front of the glaciers

Moraine

Sediment carried and deposited by a glacier

What type of moraine indicates the furthest extent of a glacial advance?

Terminal Moraine

Glacial budget

The balance, or lack of balance, between ice formation at the upper end of a glacier, and ice loss in the zone of wastage.

Ground Moraine

The flat to gently rolling plains are composed of sediment deposited from the base of the ice as ground moraine. Good soil for farming and not too susceptible to erosion.

Terminus

The front of the glacier- also called the end

Terminus- dealing with depositing material

The glacier is directly depositing dark till at its terminus. There is debris on top and along the sides of the glacier, and there is more debris inside and at the base of the glacier. If the terminus of a glacier remains at about the same place, the till piles up into an irregular mass.

Internal Shearing

The gravity pulls the ice downhill, causing the bottom part of the glacier to lag behind the upper less constrained parts. This causes the upper part to flow faster than the lower part which causes the internal shearing.

Lake Bonneville

The great salt lake in Utah in a remnant of Lake Bonneille.

Subglacial Channel

The meltwater can along the base of the glacier in a subglacial channel

Glacial Meltwater

The meltwater is heavily laden with rocks and other glacial sediment and so exerts strong erosive power on the bedrock underlying glacial sediment.

Sublimation

The process of a glacier losing more and more ice and snow by melting , wind erosion, and by the loss of ice molecules directly to the air, a process referred to as sublimation.

Active Layer

The uppermost parts of the permafrosted soil that thaws during the summer

Why do glaciers float

The water is deep enough and they are less dense than either freshwater or saltwater.

Subglacial Transport

Transport that occurs at the ice-bedrock interface, exposed in the meltwater tunnel in the photograph above.

Supraglacial Transport

Transported at the surface by ice , sometimes falling into crevasses or whisked away through melt-water tunnels

Eskers

When a glacier melts back, sediment sorted and deposited along these meltwater channels forms long, sinuous ridges.

Kettle

When an ice block melts as in the bottom diagram it creates a small depression called a kettle

Glacial Striations

When ice sheets flow across the surface and smooth/polish rocks over broad areas, usually carving a relatively smooth polished surface on to the bedrock which is gouged with scratch marks-striations.

Till

When the debris comes to a rest, and if deposited directly by ice, is unsorted which means the particles are not segregated by size and unstratified(lacking layers) masses.

Hanging Valley

When the glaciers melt away, the side valleys are higher than the main valley and we refer to one of these as a hanging valley.

Glacial grooves

When the gouge marks are large and deep, they provide evidence of subglacial erosion by dragged sediment and boulders at the base of a glacier. -glacially derived water can help carve or accentuate some glacial grooves

Neap Tides

When the moon and the sun even each other it so the difference between high tide and low tide are less than average. Deals with a quarter moon?

Why is seawater more enriched in heavy isotopes during a glacial event?

When the snow and ice accumulates on land, they tend to keep the light isotopes from returning to sea; therefor, the sea only in being enriched with mostly heavy isotopes.

Horn

When three or more cirques merge by headward erosion, it forms a pyramid like feature called a horn, Matterhorn near Zermatt, Switzerland

Glaciers and slope

Will form in gentle slopes but not steep slopes

Patterned Ground

a geometric pattern that from above the permafrost, such as polygons. It forms when expansion and contraction from frost action forms cracks or concentrates gravels, stones, or boulders at the surface. Appear and repeat over continuous and discontinuous permafrost.

Equilibrium Line mark

a gradational boundary between snow-covered ice upslope on the glacier and exposed bluish ice downslop

Medial Moraine

a sediment rich belt in the center of a glacier, forms where two glaciers join, trapping their lateral moraines within the combine glacier- may not be well preserved

Rock Flour

finely ground sediment that colors meltwater gray and is carried out to the glacier's margin, sometimes from subglacial lakes.

Recessional Moraines

form as the front of the glacier melts back and the stagnates for a while in one location, depositing a pile of sediment along the front of the glacier. Replicates the shaped of the front of the glacier when it stagnated

Currents

form when ocean of lake water flows in a certain direction. A single current can affect the entire thickness of water or currents can push a shallow water in one direction and deeper water in another.

Formations due to sea level rise

formed the many inlets and bays along the atlantic coast of the eastern US

Lateral Moraine

forms along the sides of a glacier and is expressed as a dark fringe of rocks and other debris. When the glacier melts, lateral moraines commonly form ridges along what were the edges of the glacier

Seacliffs

shorelines composed of hard bedrock can be eroded into cliffs that plunge directly into the surf or that are fronted by a narrow beach. More common in areas with tectonism, especially where the land has been uplifted.

equilibrium line

the point where the losses of ice and snow exactly balance the amount of accumulation

Pressure Melting

when the pressure is great enough, at the glaciers base, to form a think film of water.