Fluvioglacial landforms are landform

Landform

A landform or physical feature in the earth sciences and geology sub-fields, comprises a geomorphological unit, and is largely defined by its surface form and location in the landscape, as part of the terrain, and as such, is typically an element of topography...

s molded by glacial

Glacier

A glacier is a large persistent body of ice that forms where the accumulation of snow exceeds its ablation over many years, often centuries. At least 0.1 km² in area and 50 m thick, but often much larger, a glacier slowly deforms and flows due to stresses induced by its weight...

 meltwater

Meltwater

Meltwater is the water released by the melting of snow or ice, including glacial ice and ice shelfs over oceans. Meltwater is often found in the ablation zone of glaciers, where the rate of snow cover is reducing...

. This discharge of glacial streams, both over the surface (supraglacial) and beneath the ice sheet (subglacial), is higher in the warmer summer months. As subglacial water often flows under pressure, it has a high velocity

Velocity

In physics, velocity is speed in a given direction. Speed describes only how fast an object is moving, whereas velocity gives both the speed and direction of the object's motion. To have a constant velocity, an object must have a constant speed and motion in a constant direction. Constant ...

 and is very turbulent

Turbulence

In fluid dynamics, turbulence or turbulent flow is a flow regime characterized by chaotic and stochastic property changes. This includes low momentum diffusion, high momentum convection, and rapid variation of pressure and velocity in space and time...

. This high velocity enables it to transport a large amount of material which would not normally be transported in a regular stream

Stream

A stream is a body of water with a current, confined within a bed and stream banks. Depending on its locale or certain characteristics, a stream may be referred to as a branch, brook, beck, burn, creek, "crick", gill , kill, lick, rill, river, syke, bayou, rivulet, streamage, wash, run or...

 of similar size; boulders thus transported may remain as glacial erratic

Glacial erratic

A glacial erratic is a piece of rock that differs from the size and type of rock native to the area in which it rests. "Erratics" take their name from the Latin word errare, and are carried by glacial ice, often over distances of hundreds of kilometres...

s in the post-glacial terrain. As this material is transported it makes contact with the underside of a glacier and erodes vertically from below by abrasion

Abrasion (geology)

Abrasion is the mechanical scraping of a rock surface by friction between rocks and moving particles during their transport by wind, glacier, waves, gravity, running water or erosion. After friction, the moving particles dislodge loose and weak debris from the side of the rock...

. This erosion creates subglacial valley

Valley

In geology, a valley or dale is a depression with predominant extent in one direction. A very deep river valley may be called a canyon or gorge.The terms U-shaped and V-shaped are descriptive terms of geography to characterize the form of valleys...

s. When there is a decrease in discharge of the glacial steams, deposition occurs, and is responsible for large groupings of landforms like esker

Esker

An esker is a long winding ridge of stratified sand and gravel, examples of which occur in glaciated and formerly glaciated regions of Europe and North America...

s and drumlin

Drumlin

A drumlin, from the Irish word droimnín , first recorded in 1833, is an elongated whale-shaped hill formed by glacial ice acting on underlying unconsolidated till or ground moraine.-Drumlin formation:...

s in glaciated areas.

Pro-glacial lakes leave their own passive impress on the glaciated landscape, recognizable by the flatness of the former lakebed and raised terraces that mark former shorelines.

More active massive scouring occurs when ice dam

Ice dam

An ice dam occurs when water builds up behind a blockage of ice. Ice dams can occur in various ways.-Caused by a glacier:Sometimes a glacier flows down a valley to a confluence where the other branch carries an unfrozen river...

s of pro-glacial lakes fail catastrophically in a glacial lake outburst flood

Glacial lake outburst flood

A glacial lake outburst flood is a type of outburst flood that occurs when the dam containing a glacial lake fails. The dam can consist of glacier ice or a terminal moraine...

; the results can be seen, for example in the Channeled Scablands

Channeled scablands

The Channeled Scablands are a unique geological erosion feature in the U.S. state of Washington. They were created by the cataclysmic Missoula Floods that swept periodically across eastern Washington and down the Columbia River Plateau during the Pleistocene epoch. Geologist J Harlen Bretz coined...

 in the U.S. state

U.S. state

A U.S. state is any one of the 50 federated states of the United States of America that share sovereignty with the federal government. Because of this shared sovereignty, an American is a citizen both of the federal entity and of his or her state of domicile. Four states use the official title of...

 of Washington, created by the cataclysmic Missoula Floods

Missoula Floods

The Missoula Floods refer to the cataclysmic floods that swept periodically across eastern Washington and down the Columbia River Gorge at the end of the last ice age. The glacial flood events have been researched since the 1920s...

 that swept periodically across eastern Washington and down the Columbia River Plateau

Columbia River Plateau

The Columbia Plateau is a geologic and geographic region that lies across parts of the U.S. states of Washington, Oregon, and Idaho. It is a wide flood basalt plateau between the Cascade Range and the Rocky Mountains, cut through by the Columbia River...

 during the Pleistocene

Pleistocene

The Pleistocene is the epoch from 2,588,000 to 11,700 years BP that spans the world's recent period of repeated glaciations. The name pleistocene is derived from the Greek and ....

 epoch

Epoch (geology)

An epoch is a subdivision of the geologic timescale based on rock layering. In order, the higher subdivisions are periods, eras and eons. We are currently living in the Holocene epoch...

. The Shonkin Sag

Shonkin Sag

The Shonkin Sag is a prehistoric fluvioglacial landform located along the northern edge of the Highwood Mountains in the state of Montana in the United States. The Sag is a river channel formed by the Missouri River and glacial meltwater pouring from Glacial Lake Great Falls...

 along the northern edge of the Highwood Mountains

Highwood Mountains

The Highwood Mountains cover approximately 4,659 km² in north central Montana in the U.S., east of Great Falls and Benton Lake National Wildlife Refuge, at the northern end of the Lewis and Clark National Forest...

, Montana, is a channel formed by the Missouri River

Missouri River

The Missouri River flows through the central United States, and is a tributary of the Mississippi River. It is the longest river in North America and drains the third largest area, though only the thirteenth largest by discharge. The Missouri's watershed encompasses most of the American Great...

 and glacial meltwater

Meltwater

Meltwater is the water released by the melting of snow or ice, including glacial ice and ice shelfs over oceans. Meltwater is often found in the ablation zone of glaciers, where the rate of snow cover is reducing...

 pouring from Glacial Lake Great Falls

Glacial Lake Great Falls

Glacial Lake Great Falls was a prehistoric proglacial lake which existed in what is now central Montana in the United States between 15,000 BCE and 11,000 BCE. Centered on the modern city of Great Falls, Montana, Glacial Lake Great Falls extended as far north as Cut Bank, Montana, and as far south...

; it is one of the most famous prehistoric meltwater channels in the world.