Leech Lake – How the lake was born.
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Article by Steve Henry, Cass County Environmental Services Department. This is an expanded version of the article published in the Leech Lake Association newsletter in May 2025.
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Leech Lake is a fantastic resource providing many types of recreation year round. As one of the top ten walleye lakes in Minnesota Leech Lake attracts anglers from around the United States. The perch, crappie, whitefish, and bass fisheries are also excellent and anglers enjoy their time on the lake. At 111,527 acres Leech Lake is the 3rd largest lake within Minnesota providing a huge amount of area to recreate with many bays and eleven islands for families to explore. The views from the lake are exceptional with a significant portion of the shoreline in public or tribal ownership and maintained as mature pine and hardwood forest with significant hills along the southern shoreline.
Leech Lake changes every year with new homes being built and remodeled, changing amounts of vegetation in the lake, boat and dock sizes increasing, variation in fish populations and distribution, and new species occasionally invading the lake. These changes that we observe are overlayed on a larger format that includes the lake’s depth
profile, bottom composition, and surrounding environment all of which are due to the actions of glaciers that traversed this area 12,000 to 27,000 years ago. We often live in the finer details without noticing those larger events that formed the dramatic landscape surrounding us.
The first major land forming event recognizable around Leech Lake is the advance of the Itasca Lobe of glacial ice from the north around 19,000 years ago. The ice was over a thousand feet thick and pushed slowly across the landscape. Th Itasca Lobe interacted with the Brainerd Lobe of ice which was advancing from the northeast at the same time.
The front edge of both lobes stalled with their junction near Walker and the advance of ice from behind continued to bring material forward forming large terminal moraines which are thick deposits of mixed sand, gravel, and rocks. The Itasca moraine trends east-west and is visible west-northwest of Walker as a large line of hills extending to the area north of Park Rapids and including the Itasca State Park area. The Brainerd moraine extends north-south and is visible starting north of Ten Mile Lake and extending south to the east of Hackensack, Backus, and on to Brainerd. The moraine formed by the edges of the two glacial lobes interacting extends east of Walker towards Remer and State Highway 200 generally follows the northern edge of that moraine. Webb Lake, Woman Lake, Big Deep Lake, and Little Boy Lake are all along the southern edge of this moraine.
Leech Lake changes every year with new homes being built and remodeled, changing amounts of vegetation in the lake, boat and dock sizes increasing, variation in fish populations and distribution, and new species occasionally invading the lake. These changes that we observe are overlayed on a larger format that includes the lake’s depth
profile, bottom composition, and surrounding environment all of which are due to the actions of glaciers that traversed this area 12,000 to 27,000 years ago. We often live in the finer details without noticing those larger events that formed the dramatic landscape surrounding us.
The first major land forming event recognizable around Leech Lake is the advance of the Itasca Lobe of glacial ice from the north around 19,000 years ago. The ice was over a thousand feet thick and pushed slowly across the landscape. Th Itasca Lobe interacted with the Brainerd Lobe of ice which was advancing from the northeast at the same time.
The front edge of both lobes stalled with their junction near Walker and the advance of ice from behind continued to bring material forward forming large terminal moraines which are thick deposits of mixed sand, gravel, and rocks. The Itasca moraine trends east-west and is visible west-northwest of Walker as a large line of hills extending to the area north of Park Rapids and including the Itasca State Park area. The Brainerd moraine extends north-south and is visible starting north of Ten Mile Lake and extending south to the east of Hackensack, Backus, and on to Brainerd. The moraine formed by the edges of the two glacial lobes interacting extends east of Walker towards Remer and State Highway 200 generally follows the northern edge of that moraine. Webb Lake, Woman Lake, Big Deep Lake, and Little Boy Lake are all along the southern edge of this moraine.
Orange areas are End Moraine formed at the front edge of glacial ice.
As this ice melted and began to retreat huge amounts of water gathered below the ice under great pressure and searched for an outlet. This pressurized meltwater lubricated the base of the glacier and lifted recently deposited sediments that overlay a preexisting drainage channel. This combination caused a glacial surge which shoved a block of the moraine, the Shingobee block, forward and on top of the material in front of it. This created the high hills on the south side of Walker which you can drive over by using the Ag Gwah Ching cutoff road County 37 NW from it’s junction with State Highway 34 south of Walker over to State Highway 200 southeast of Walker. These hills are prominently displayed when driving into Walker from the east on State Highway 200. Around two miles east of the Moondance property State Highway 200 drops off of the higher moraine and travels across a flat area which was a portion of Leech Lake during a higher lake level. The Shingobee block is visible as the high hills on the horizon in front of you.
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This sketch from Glacial Geology of the Shingobee River Headwaters Area, North-Central Minnesota Scientific Investigations Report 2013–5165 illustrates how the
Shingobee block was shoved from the bottom of Walker Bay to form the hills south of Walker and how the drainage channel passed to the west of the block.
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The Shingobee Block is visible in this hillshade view just south of Walker. The ridges that run south at one time aligned with the ridges to the west.
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The pressurized meltwater exploited an earlier preexisting meltwater channel and blew an outlet through the Itasca moraine on the west edge of Walker along the western side of the Shingobee block. The deep channel scoured by this event is now occupied by the chain of lakes including May Lake, Long Lake, Lake Alice, Big Bass Lake, Eleventh Crow Wing, and several of the other Crow Wing Lakes down to 5th Crow Wing Lake. This channel is visible in air photos as a chain of lakes extending more than 20 miles from Walker. The sand and gravel washed from this channel buried much of southern Hubbard County in a outwash fan leaving a flattened landscape. As the glaciers melted in place the pressurized water scoured deep channels to the north under the ice, forming tunnel valleys extending northwest through Kabekona Lake and Kabekona Bay up to Lake Bemidji, north through Steamboat Bay and through Cass Lake, and northeast through Sucker and Portage Bays
and through Lake Winnibigoshish. Water drained through these channels from as far away as Red Lake. At that time those channels were likely nearly as deep as Walker Bay is now, more than 100 feet deep.
and through Lake Winnibigoshish. Water drained through these channels from as far away as Red Lake. At that time those channels were likely nearly as deep as Walker Bay is now, more than 100 feet deep.
These lakes formed as ice blocks buried within the deep channel carved by meltwater escaping from the Leech Lake basin as the Itasca Lobe melted. As meltwater waned the ice blocks were deeply buried is sand and gravel before melting into basins. As this drainage phase of the Itasca Lobe waned water pooled southeast of Walker in the Akeley area. Hills left by the powerful meltwater flows blocked this water from flowing back towards Leech Lake. The southern edge of the Shingobee Block was a loose unconsolidated material and eventually the pooled water burst through and catastrophically formed the Shingobee River channel draining around 132 trillion gallons of water back into Leech Lake and leaving the deep trench now visible from County Road 50 near the North Country Trailhead there.
County Road 50 south of Walker crossing the Shingobee River channel.
Around 16,000 years ago ice readvanced from the northwest as the Koochiching Lobe. This lobe passed just north of Leech Lake before curving south along the eastern edge of Leech Lake. A minor push from the east by this lobe formed the high hills east of Longville just past Inguadona Lake. Behind this moraine of the Koochiching lobe lie the
Trelipe Lakes and Thunder Lake. As this ice melted Leech Lake rose to a high level, called a high stand, and water escaped to the south through several channels some of which are now occupied by creeks and rivers that flow back in the opposite direction in the present day. Cedar Creek and the Boy River are prominent examples of this glacial meltwater formed channels. South of Whipholt Bay is another area where meltwater escaped to the south. The area of Whipholt was planed flat by wave action during the high stand of Leech Lake as was the area south of Jack Lake two miles eat of the Moondance property. The
sand and gravel washed from these channels traveled south building hills around Webb Lake, leaving abandoned stream bottoms ‘eskers’ between Baby and Mann Lakes and in several other areas, and flattened the area east of Longville especially around Inguadona Lake. Large amounts of sand and gravel washed directly into the northern portions of the Leech Lake basin smoothing the terrain to the north and filling in northern Steamboat Bay, Sucker Bay, Portage Bay and even portions of the main lake basin north of Pelican Island.
These sand and gravel deposits filled in much of the deep channels that had been formed leaving Kabekona and Walker Bays as the two deep areas of the lake and the Paris Trench and other areas along the southern shoreline as the remaining deep water features in the main basin. Eventually the Koochiching lobe retreated and meltwater escaped to the east forming the Leech Lake River channel and establishing the drainage pattern we have today.
A cold dry period followed the retreat of the Koochiching lobe dropping the level of Leech Lake and allowing wind to scour the lake bottom. During this time sand blown from the lake covered much of the area east to Remer and sand dunes were formed in a band from the south side of Lake Winnibigoshish down along the east side of Leech Lake past Federal Dam. This wind scouring removed sand but left behind rocks that are prominently visible around many islands, along underwater bars, and along the shorelines. Ice action
also transported rocks away from the lake center and deposited them along the shorelines. Some sunken islands represent drainage from the glacial ice surface through holes and
into the lake basin. These kames as they are known are most common in Walker Bay and are visible as piles of rocks and gravel often so steep that they are near the point at which they would naturally collapse and slide, this is known as the angle of repose. These kames can form under or beside glaciers from material carried off the ice by meltwater and are prominent features in many glacial landscapes.
Trelipe Lakes and Thunder Lake. As this ice melted Leech Lake rose to a high level, called a high stand, and water escaped to the south through several channels some of which are now occupied by creeks and rivers that flow back in the opposite direction in the present day. Cedar Creek and the Boy River are prominent examples of this glacial meltwater formed channels. South of Whipholt Bay is another area where meltwater escaped to the south. The area of Whipholt was planed flat by wave action during the high stand of Leech Lake as was the area south of Jack Lake two miles eat of the Moondance property. The
sand and gravel washed from these channels traveled south building hills around Webb Lake, leaving abandoned stream bottoms ‘eskers’ between Baby and Mann Lakes and in several other areas, and flattened the area east of Longville especially around Inguadona Lake. Large amounts of sand and gravel washed directly into the northern portions of the Leech Lake basin smoothing the terrain to the north and filling in northern Steamboat Bay, Sucker Bay, Portage Bay and even portions of the main lake basin north of Pelican Island.
These sand and gravel deposits filled in much of the deep channels that had been formed leaving Kabekona and Walker Bays as the two deep areas of the lake and the Paris Trench and other areas along the southern shoreline as the remaining deep water features in the main basin. Eventually the Koochiching lobe retreated and meltwater escaped to the east forming the Leech Lake River channel and establishing the drainage pattern we have today.
A cold dry period followed the retreat of the Koochiching lobe dropping the level of Leech Lake and allowing wind to scour the lake bottom. During this time sand blown from the lake covered much of the area east to Remer and sand dunes were formed in a band from the south side of Lake Winnibigoshish down along the east side of Leech Lake past Federal Dam. This wind scouring removed sand but left behind rocks that are prominently visible around many islands, along underwater bars, and along the shorelines. Ice action
also transported rocks away from the lake center and deposited them along the shorelines. Some sunken islands represent drainage from the glacial ice surface through holes and
into the lake basin. These kames as they are known are most common in Walker Bay and are visible as piles of rocks and gravel often so steep that they are near the point at which they would naturally collapse and slide, this is known as the angle of repose. These kames can form under or beside glaciers from material carried off the ice by meltwater and are prominent features in many glacial landscapes.
These rocks on the north side of Pelican Island are a combination of lag rock left behind by scouring winds at a lower lake level and recent ice action.
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One of the most recent lake forming changes was the installation of the dam on the lake outlet. This dam was installed between 1882 and 1884 by building a 2,600 foot embankment and 1,000 feet of timber dam on a pile structure. By 1903 the logs had rotted away and there were replaced with reinforced concrete. This raised the lake level by just over seven feet inundating many Native American villages, graveyards, rice beds, and portages devastating those local communities. The three bodies discovered along the
Leech Lake shoreline last summer in August were eroded from a flooded Native American graveyard. This flooding on Native American communities and resources precipitated a centuries long conflict between the tribe and United States government. The increased water level allowed logging around the lake to proceed rapidly and through 1920 the log
sluiceway in the dam was regularly operated to move logs downriver. Many originally tribal lands were incorporated into the Chippewa National Forest during this time period through questionable land transfers.
Leech Lake shoreline last summer in August were eroded from a flooded Native American graveyard. This flooding on Native American communities and resources precipitated a centuries long conflict between the tribe and United States government. The increased water level allowed logging around the lake to proceed rapidly and through 1920 the log
sluiceway in the dam was regularly operated to move logs downriver. Many originally tribal lands were incorporated into the Chippewa National Forest during this time period through questionable land transfers.
Rebuilding the original log dam with concrete in 1901.
The Leech Lake we see today was formed by huge disturbances thousands of years ago. Much of what we observe are the small changes that occur in recent years but the
backdrop of the lake is remnants of thousands of years of dynamic earth movements. Enjoy your days on and around the lake recreating and as you do take a moment to reflect on the larger landscape, those huge impacts that have occurred, and their importance in this resource we all treasure.
backdrop of the lake is remnants of thousands of years of dynamic earth movements. Enjoy your days on and around the lake recreating and as you do take a moment to reflect on the larger landscape, those huge impacts that have occurred, and their importance in this resource we all treasure.