Gifts of the Glaciers

Glacial Landforms

Gifts of the Glaciers

 Moving ice of glacier was responsible for water, landforms, and soil characteristics and patterns of today  Sculpturing of bedrock materials  Erosion of bedrock  Deposition of glacial drift

Glacial Landforms

 Glacial landforms dominate the Great Lakes region  Northeastern Illinois  Northwest Indiana  Most of WI, MI, MN, and Ontario

Glacial Landforms

 Effects of moving ice:  Leveled off the existing hills  Filled in valleys  Blocked the drainage of the rivers  Gouged out major basins (ex: GLB)  Processes involved: grinding, erosion, leveling, and depositing.

Glaciers perform, in many ways, like an excavator. Although they can push weak material, like gravel, like a bulldozer blade, they are far more likely to lift material out of place, like a backhoe, or scratch it in place, like a ripper. And, like a bulldozer, glaciers are poor at eroding rock unless it is already weakened.

Glacial Erosion

 Rock Failure:  The first step in glacial erosion is rock failure.  Water, ice causes cracks in rocks

Glacial Erosion

 Two main types of glacial erosion 

Plucking

(analagous to a backhoe). 

Abrasion

 Plucked debris in basal ice grinds into the bedrock, just like sandpaper across wood

Plucking

Abrasion

Glacial Erosion



Glacial / Fluvial Processes

: At the bed of warm based glaciers, water is present in it’s fluid state.  This water flows underneath the glacier and assists erosion by removing erosional products, especially silt.

 When water collects into subglacial channels, it can be sufficiently powerful to erode by itself

Subglacial view of basal debris

Glacial Outwash Stream

Glacial Outwash Stream

Glacial Landforms

 Material deposited by glaciers is called

drift



Till

is deposited directly from glacier 

Outwash

is deposited by meltwater  In summer, meltwater carried along “rock flour sediments  In winter these were blown by wind  Left thick beds of

loess

valleys downwind from major river

Glacial Drift

Till that has melted out from the dark striped basal ice layer.

Glacial Till – North Shore L. Superior

Outwash plain Outwash plain and braided streams

Outwash sediments

Till exposure (dark tan) located above outwash sediments (light tan)

Glacial Grooves on Kelleys Island, Ohio

Glacial Striations on Canadian Shield Bedrock

Large Glacial Erratic

Large Glacial Erratic

Glacial Landforms

 Rock, gravel, sand, and silt left behind by melting glaciers formed mounds, ridges, and thick windblown deposits. 

Moraines

mark re-advances of glacier and when glacier stalled as it retreated  Accumulated drift is pushed into higher mounds by ice

Glacial Landforms



End Moraines

— During periods when the rate of ice advance nearly equaled that of melting, huge mounds of sand and gravel piled up in curved ridges along the glacier's edge.

Ground Moraine End Moraine

End Moraines

Valparaiso morainic system Marseilles morainic system The end moraines from the Wisconsin glaciation can be seen in Northeastern Illinois.

Illinois Moraines

Glacial Landforms



Ground Moraines -

Ground moraines are formed as till is deposited directly beneath a glacier; between the ice and the underlying rock.

 Ground moraines are located behind end moraines.  Form gently rolling to flat countryside.

Ground Moraine End Moraine

Ground Moraine

Ground Moraine

Ground Moraine with Kettles

Moraines

 End moraines - western suburbs of Chicago  Form at melting end of glacier as till piles up  Belts of rolling or rugged hills with intervening swales, swamps and lakes  Ground moraines - DeKalb county  Form as ice front retreats and leaves a flatter deposit  Gently undulating lands

Ground Moraine End Moraine

Moraines

 Recessional moraines are formed when the ice stands still and melts.

Recessional Moraines

Moraines



Push Moraine -

A ridge or pile of unstratified glacial sediment that is formed in front of the ice margin by the terminus of an advancing glacier, bulldozing sediment in its path.

Kettles



Kettles

— Depressions formed when ice broke into chunks that became buried in sediment.  When the ice block melted, it left a depression, which sometimes filled with water to form kettle lakes.  Kettle lakes are common in northern and central Illinois.

Ice Block/Kettle Hole Lakes

 Kettle Hole Lakes  These are usually deep lakes  Many still have water  Steep sides  Most Great Lakes region lakes are kettle hole lakes  Minnesota = Land of 10,000 Lakes  Volo Bog formed in a kettle

Volo Bog

Iceland – Kettle forming with ice block still in place.

Kettle within Morainal Ridges

Outwash Plains



Outwash Plains

— At the glacial front, water flowing from underneath the ice formed level plains of fine sediment.

Outwash plain Outwash plain and braided streams

Drumlins



Drumlins

are low, smoothly rounded hill of compact glacial till, built under the margin of the ice and shaped by its flow  Sculpted by active ice during a re-advance over an old till plain  Arranged more or less parallel  Separated from each other by poorly drained troughs or

swales

Drumlins

The Antrim-Charlevoix drumlin field is one of the largest in the midwest.

Drumlins at Kejimkujik Provincial Park, Nova Scotia, CA

Drumlin Fields along coast of Michigan

Drumlins near Auburn, New York, looking southeast. Owasco Lake is in the upper right

Eskers



Eskers

are long narrow hills that look like abandoned railway embankments  Long, winding ridges of sand and gravel formed in waterways under the glaciers.

 Long narrow winding ridges of stratified gravel, sand and silt  Formed under stagnant rather than moving ice  Form low, sinuous hills that can stretch for miles and often resemble snakes when seen from the air

Eskers

Esker

Esker

Esker cross-section. Eskers are often mined for gravel

Kames



Kames -

Smaller mounds of sand and gravel formed where sediment filled cracks in the ice.

 Stratified hills of cobble, gravel, sand, and silt  Formed when meltwater plunges into crevasses/ moulins on the ice surface or at the ice front and deposits its load of sediment  Conical (more or less) sometimes ridgelike in shape  Series of kames at Glacial Park in McHenry Co.

Kames

A moulin (glacier mill) on a modern glacier

Prairie Kame in Kane County

Camelback Kame at Glacial Park, McHenry Co. Illinois

Moulin Kame in the Kettle Moraine, 4 miles northeast of Dundee, WI. Conner Hill, looking southwest

Glacial Soils

 Regional soils are also the result of glacial deposits  Nonglaciated areas  Driftless area of SW WI  Limestone bedrock exposure areas of sw Cook and western Will counties  Ice picks up rocks and other debris  Ice grinds rock bedrock into fine silty deposits called “rock flour” or loess (luss)

Loess Deposits



Loess Deposits

— During the cold seasons, the flow of glacial meltwater slowed. Fine silt that had been deposited on the outwash plain and along river channels leading from the glacier was exposed and dried out. Winds blew the dust to surrounding areas where it slowly grew into thick silt deposits called loess. Vertical faces of loess, sometimes over 30 meters (about 100 ft.) high, can be seen along the Mississippi and Illinois River valleys.

Loess bluff near Edwardsville, IL.

Illinois loess deposits

Glacial lake plains

   Sediments of glacial and proglacial lakes, also river sediments that flowed into lakes May have sand dunes far from any modern water source  Beach ridges  Visible at Indiana and Illinois Dunes Often have special soils  Marl (calcium carbonate: mined for cement and fertilizer)  Special crops farmed on these soils  Navy beans  Sugar beets  Soy beans

Glacial Lake Plain Bounded by Moraine