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Parts of a Division A Study Guide- Part 2

• Zones of a glacier

Zone of Accumulation: The region where snowfall adds to the glacier. It occurs where the remains enough year-round so that winter does not melt or sublimate away entirely during the summer. Zone of : The region where ablation subtracts ice from the glacier through or sublimation. Equilibrium Line: A boundary between the zone of accumulation and ablation controlled by elevation and . Head: The uphill, top end of a glacier. Terminus: The downhill, bottom end of a glacier. Snowline: The area between the summer melting and accumulation area where the snow lasts from season to season.

Brittle Zone: are common in this zone. Brittle-Plastic Transition (dotted line): A line between the brittle and plastic zones at about 60m. Deep, because ice cannot crack below that. Plastic Zone: Ice cannot crack in this zone.

• Types of

Glacial : A stripe of debris or dropped by a glacier. Lateral Moraine:A stripe of debris along the side of a glacier from sediment dropped on the surface from its edge. Medial Moraine: A stripe of debris in a glacier constituting two lateral moraines from when two glaciers merge. End/: A stripe of sediment accumulated at a glacier’s toe that has been built up. Recessional Moraine: A secondary terminal moraine deposited during a temporary glacial standstill during its retreat. Ground Moraine: An accumulation of lodgment at the base of the ice deposited as the glacier retreats. They often form small or and may be turned into a by overriding ice.

• Ice within a glacier

Fresh Snow: It contains up to 90% air and is very loosely packed. Its density is about 0.1 g/cm3 : It is snow that persists for an entire year and has a density of about 0.6 g/cm3 Glacial Ice: It forms at a depth of about 50 meters deep and has a density of about 0.9 g/cm3

• Characteristics of a glacier

Pyramidal Peak (1): It is a sharp, triangle shaped peak with the faces separated by . (2): It is a sharp between two of corries. /Corrie (3): It is a bowl-shaped hollow with steep sides and back filled with ice. (4): It is when a forms in a in the floor of a cirque. (5): It is a fan shaped pile of or debris washed down by the and piled up where the valley side joins the valley floor. (6): It is a long and narrow lake in a valley carved by a glacier. Truncated Spur (7): It is a ridge formed from where a glacier cut sharply through the valley. Misfit Stream (8): A stream in the valley that is too small to have formed the valley on its own. Hanging Valley (9): It is where the valley floor is higher than the main valley’s floor. U-shaped Valley (10): A valley cut by a glacier with steep sides and a relatively floor

Crevasses: A deep crack or fracture in a or glacier. Sun Cups: Bowl-shaped depressions on the surface of a glacier that form from the uneven heating of the surface of the glacier of . Cryoconites: A powdery windblown dust made of a combination of small rock particles and other material which is deposited and builds up on snow. : A type of natural cave that contains significant amounts of perineal ice year round. : A circular opening in the ice that allows to enter from the surface. Striations: Horizontal scratches or gouges cut into the by . Chatter Marks: Crescent-shaped marks left by the chipping of the bedrock through . Nunataks: An isolated peak of rock projecting above the surface of the ice. Snake Coils: Essentially miniature tunnel valleys, they are a snake coil-like shaped that occur along some ablation lines. Melt : Pools of open water that form on (and sometimes under) ice in and summer. Tunnel Valleys: a large, long, U-shaped valley originally cut under the glacial ice near the margin of continental ice sheets

Types of Glaciers Division A Study Guide

Mountain/Alpine Glaciers: Also known as alpine glaciers, they exist and ranges and generally move from high to low elevations. Cirque Glacier: It is a bowl shaped hollow filled with ice. Mountain Ice Cap: It is a mass of ice that covers less than 50,000 km2. Piedmont Glacier: They are fans or lobes of ice that form where a valley glacier spreads out to the adjacent . Valley Glacier: They are of ice that flow downstream. : valley glaciers that protrude out into the as they elongate. Continental Glaciers/Ice Sheets: They are vast ice sheets that spread over thousands of kilometers of continental crust (must be greater than 50,000km2). • : the northernmost part of the mainland • West (Lesser Antarctica): a segment of the Antarctic ice sheet on the side of the Transantarctic (Greater Antarctica): a segment of the Antarctic Ice Sheet on the east side and the largest ice sheet in the world Temperate Glaciers: They occur where atmospheric become warm enough for the glacial ice to be around its melting temperature throughout the year. Polar Glaciers: They occur in regions where atmospheric temperatures stay cold enough year round that the ice remains below melting temperature throughout the year. Tidewater Glaciers: Glaciers that flow out out into sea along the . Ice Shelves: Broad, flat sheets of ice from continental glaciers entering the sea. Ice Fields: A large area of interconnected glaciers (usually found in mountainous regions). Ice : A region of an ice sheet that moves significantly faster than the surrounding ice. Rock Glaciers: Distinctive consisting of something between angular rock debris frozen in interstitial ice and former true glaciers overlain by a layer of talus.

Formation/Maintenance of Glaciers Division A Study Guide

• Solar Variability A change in the amount of produced by the sun

Solar Cycle: • Duration of 11 years from minimum to minimum • Maximum is with maximum sunspots, while minimum is the opposite • Most notable difference in temperature and ozone in the stratosphere • Discovered by Samuel Heinrich Schwabe in 1843 • Counted by Wolf Index

Magnetic Cycle: • Sunspots occur at different during different parts of the cycle • Sunspots are strongly magnetized • The magnetic polarity of sunspot pairs is: o Constant in a cycle o Opposite across the equator in a cycle o Reversed from one cycle to the next • Since the cycle reveses, it takes 22 years for it to return to its original state • The sun’s magnetic field is generated by the solar dynamo • Studied by George

Sunspots: • Dark spots on the surface of the sun • Regions of reduced surface temperature that emit more heat • Caused by concentrations of magnetic field flux which create convection • The closer they are to the equator, the closer it is to a solar minimum • First appear at mid-latitudes • Move towards the equator until a solar minimum occurs (then the cycle reverses)

Maunder Minimum: • A time of very few sunspots that spanned from 1645 to 1715 • Coincided with the middle of the little that occured in and • Previously thought to have caused the (new research shows that there was also an increase in volcanic activity at the time) • Named after Edward Walter Maunder after he extensively studied the event

• Insolation Amount of the sun’s energy that strikes ’s surface

• Milankovitch Cycle: The collective effects of the changes in the Earth’s movement on its over thousands of years o Based on the following changes: • Eccentricity: Earth’s orbital path around the sun o 1,000 year cycle from one orbit to another and back again • Obliquity: Variation in the tilt of Earth’s axis over a 41,000 year cycle o Moves from 22 to 25 degrees o 41,000 year cycle from one tilt to another and back again • Precession: Wobble of Earth’s axis o 19,000 to 26,000 year cycle

• Dust • Particles from Earth’s surface carried into the atmosphere o Includes wind-eroded dust, volcanic particles (dust and gas), fires, etc • Dust particles reflect incoming solar ultraviolet rays back to space, causing Earth’s surface to cool

• Greenhouse Gases Gases that absorb heat and raise the temperature of the atmosphere (can be natural and anthropogenic) • Water vapor: the most abundant ; the warmer the atmosphere, the more vapor it can hold • : released into the atmosphere through burning of and fuels • Methane: primary component of natural gas (used in houses for heat) • Nitrous oxide: naturally present in the atmosphere through the nitrogen cycle • Tropospheric Ozone: when pollutants break up the ozone layer, creating more tropospheric ozone • CFCs: a harmful pollutant once used in refrigerators and aerosols

• Ocean Circulation The North Atlantic Deep Water Current is one long, continuous ocean current that takes about 1000 years to complete (The Great Conveyor)

• The warmer water from the equator rises, while the colder water from the poles sinks • The more saline water sinks (it is more dense), while the less saline water rises o When glaciers melt, the water has a lower salinity, disrupting the current

Ice that originates in the ocean from the ocean water freezes • Reflects incoming solar radiation ( of about 95%) • Blocks ocean water from sinking, thus preventing thermohaline circulation of ocean currents

Glacial - Depositional Features Division A Study Guide Ice Rafted Debris: Rock material carried away by ice and Erratic: Rocks transported through glaciers actions placed into areas of differing rock types Terraces: Debris deposited between glaciers and valley walls form conical, hilly deposits Till: Deposits formed underneath glaciers plastered down by moving ice as it drags debris across the surface. : Superglacial material from the surface of a glacier carried through a moulin and into the glaciers plumbing system forming long snake-like (sinuous) ridges from the meltwater of a retreating glacier : Material accumulates under a glacier, ix covered with till, and then reshaped into an elongated ridge; indicate the relative direction of the flow of the glaciers at the time they were formed Moraines: piles of rock material that have eroded from the valley walls and pushed to the front and sides of a glacier (see parts of a glacier) Glacial Flour (): Consists of fine-grained, -sized particles of rock; can accumulate in a lake, turning the water a turquoise-blue color

Stratified: Heavier debris is dropped earlier than lighter debris, so the deposit is layered (stratified deposits are carried by water)