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Geology of the Adirondack Park
The Adirondack Mountains are very different in shape and content
from other mountain systems. Unlike elongated ranges like the Rockies
and the Appalachians, the Adirondacks form a circular dome, 160
miles wide and 1 mile high.
Although the Dome as we know it today is a relatively recent development, having
emerged about 5 million years ago, it is made of ancient rocks more than a
1,000 million years old. Hence, the Adirondacks are "new mountains from
Birth of a Glacier
A quarter of a million years ago, when the earth was a few degrees
cooler, the snow which fell in the winter did not melt entirely
in the cool summers. As it accumulated over millennia, its enormous
weight compressed the lower layers of snow into ice, eventually
becoming thousands of feet thick. The increased pressure softened
the lower ice, causing it to flow like thick molasses. A glacier
Shaping the Landscape
As the ice advanced southward into the Adirondack region, soil
and rock was scraped from the land and embedded in the ice like
sand in sandpaper. Alternately scratching and smoothing the earth's
surface, the glacier pulverized boulders into pebbles, carrying
the debris as it moved. As it thickened, the glacier crept over
hills and, eventually, over the highest mountains, breaking and
lifting rocks as it rounded their summits. When the ice sheet melted,
these rocks, called erratics, were deposited throughout
the Adirondacks, where they can be seen today in fields, along
forest trails, and scattered on mountaintops.
Alpine Glaciers, Cirques, and Horns
As the massive continental glacier grew to the north, small alpine
glaciers were forming in the Adirondack Mountains. These alpine
glaciers carved the upper slopes of the mountains for thousands
of years. Gradually, they became buried by the advance of the continental
The distinctive summit of Whiteface Mountain owes its shape to alpine glaciers.
Bowl-shaped amphitheaters called cirques were carved from the rock on the north,
east and west sides of the mountain by three separate alpine glaciers. Where
the tops of the cirques joined, sharp ridges, called aretes, were formed. If
this process had continued, the cirques would have ended up back-to-back, leaving
a horn, and Whiteface Mountain would now look like the Matterhorn in Switzerland.
Kettle Holes & Kettle Ponds
As the glacier thawed, iceberg-sized chunks of ice broke off and were buried
beneath accumulating sand and gravel washed from the ice. When these ice blocks
melted, they left depressions - kettle holes - in the landscape. When a kettle
hole went below the water table, a kettle pond was established as the steady
supply of water remained in the basin. Many of the small, circular ponds and
wetlands in the Adirondacks were created in this fashion.
Eskers and Kames
Meltwater streams, flowing under and within the glacier through
tunnels in the ice, built their own stream beds from rock material
embedded in the glacier. After the glacier melted, these riverbed
sediments were deposited on the landscape as winding ridges called
eskers. When sediment-laden water flowed over the glacier's surface,
it filled depressions with sand and gravel.
As the glacier melted, material from circular depressions was deposited on
the landscape as mounds called kames.
Adirondack soils are young, having developed only since the glacial
retreat about 10,000 years ago. Unglaciated areas in the rest of
the United States have soils that have developed over millions
of years. Soils in the Adirondacks are generally thin, sandy, acid,
infertile, and subject to drought.
Forest soils have a layer of leaves, needles, twigs and other
plant and animal parts covering the mineral soil. This organic
debris accumulated with every season and, as it slowly decomposed,
it recycles nutrients back to the growing plants. The mineral soil
provides plants with solid anchorage for their roots and a secondary
source of nutrients. Tree roots will grow in all directions within
the soil in search of water, nutrients and support. Root growth
will continue as long as the soil temperature is greater then 40
degree F and roots are not limited by rock or compacted soil, or
by soil so water-saturated that it contains no oxygen for the roots.
The melting ice sheet created huge, sediment-laden rivers that
roared across the Adirondacks, depositing sand and gravel outwash
on giant, shifting floodplains. Coarse gravels and boulders settled
on river bottoms; lighter sand particles, silts and clays were
carried downstream. As the glacial rivers changed velocity and
direction, layers of these various outwash materials built up on
top of one another, forming the sedimentary strata normally found
in valleys and lower elevations today.
The debris that was deposited directly on the land by melting
glaciers without being carried and stratified by meltwater streams
contained unsorted rocks of all shapes and sizes. These are referred
to as till. Because they have not been smoothed by the movement
of the meltwater stream, till materials are often rough and jagged.
Four Basic Ingredients
Soil is made up of four components: mineral and rock particles,
decayed organic matter, live organisms, and space for air and water.
Minerals and Rocks
The mineral component of soil ranges from fine clays to rocks.
The upper mineral layer - topsoil - may have organic matter incorporated
into it. The lower mineral layers, or horizons, are collectively
called the subsoil.
Dead plants and animals and their waste products, in varying
stages of decomposition, provide the organic component of soil.
These horizons exist near the top of most forest soils.
From microorganisms - bacteria, fungi, and protozoa to earthworms,
soil organisms may account for 5 tons of living tissue per acre.
These organisms aid in the essential enrichment of soil by destroying
plant residues, decomposing the dead bodies of all organisms, and
mixing and granulation soil particles.
Healthy soil promotes the recycling of nutrients from mineral
and organic material to live organisms. This transfer occurs in
the voids between materials in the soil, in the spaces for air
and water, often called, collectively, pore space. Typically, topsoil
has 50 percent pore space in its mix of organic and mineral materials.
Growing conditions are ideal when soil pore space holds equal parts
of air and water, allowing room for root expansion, diffusion of
nutrients, and movement of soil life.
Soils are formed by the action of plants and animals and the
physical breakdown of minerals, called weathering.
Plant and animal material which accumulated on the surface of the ground is
decomposed by numerous micro-organisms. The by-products of the process are
organic acids that are washed into the ground, making the soils acidic. These
acids dissolve and transport organic matter, iron, and other elements into
the soil, to a depth of one or two feet on the better drained sites.
Organic matter accumulates to form blackened layers in the soil; below, iron
accumulates to form red/rusty colored layers.
Formation of Water Systems
Melting ice, glacial debris, and changing glacial topography
contributed to the continual disruption of the meltwater drainage
system of the Adirondack region. Lakes and ponds were formed as
ice debris dammed river valleys; as dams broke, sand and gravel
were redistributed downstream. This process left glaciated regions
like northern Minnesota, Wisconsin, and the Adirondacks dotted
with thousands of beautiful, natural lakes. Yet for all this reconfiguration
of the landscape, the major drainage patterns of the Adirondack
Dome were essentially unchanged by glaciation. Taking the path
of least resistance, Adirondack waters drain from the central high
country to the region's periphery. Water flows east from the mountains
to Lake Champlain, northwest to the St. Lawrence River, west to
Lake Ontario, and southward to the Hudson and the Mohawk rivers,
as it did before the arrival of the glaciers.
Rivers and Streams
Water is both the workhorse of the sun and the lifeblood of the
living world, flowing in an endless cycle through the landscape.
Continually replenished in flakes of snow, drops of rain and dew,
or moisture condensed into clouds and fog, water links all the
plant and animal communities of the Adirondack Park. Wherever it
falls to earth, water moves downhill in response to gravity. Rivulets
and trickles join brooks, which combine to form streams and rivers.
Nearly 30,000 miles of streams and brooks that emerge from the
mountains and forests form the network from which 1,000 miles of
powerful Adirondack rivers gather their volume and strength. These
rivers and their networks are perhaps the greatest multiple-use
natural resources in the Adirondacks. They provide habitat for
fish and wildlife from the kingfisher to the salmon to the otter.
In the past, they were the vessels of transport for pulp and provided
for sawing logs into lumber for market. They also were the trade
and travel corridors that set the pattern of settlement of Adirondack hamlets
that we still see.
Riffles and Pools
In their mountainous headwater reaches, most streams fall steeply
through narrow v-shaped channels in the shallow soil and bedrock,
developing swift-running riffles that alternate with deeper, more
sluggish pools. Riffles, places of high energy where air and water
freely mix, charge stream water with oxygen. Pools are quieter
areas where organic materials tend to collect and decompose, consuming
oxygen in the process. This allows the vital recycling of nutrients
necessary for living organisms in the stream. One after another,
watershed streams join force, forming rivers that link the mountains
with the sea.
The river carries sediments eroded from the hills down to the flatland, where,
as it slows and meanders, it deposits its bounty in the slack water of bends
or along the floodplain. Lakes and Ponds Flowing and still water has always
been an integral part of the Adirondack landscape. But the lakes and ponds
we know today are relatively young, resulting from the retreat of the last
glacier, the Wisconsin, only 10,000 years ago. Each lake and pond is a separate
ecosystem composed of a community of plants, animals and microbes living together
in a stillwater environment.
Ponds are typically shallow enough for sunlight to reach across their entire
bottom; lakes usually fall off into darkness, where rooted aquatic plants cannot
grow. Coldwater lakes are often deep and clear, with steep sides and rocky
or sandy bottoms. Because light does not penetrate all the way to the bottom,
relatively little plant growth takes place. Warmwater ponds are typically shallower,
with gently sloping sides and thicker, organic-rich sediments. Their shoreline
offers a fertile environment for aquatic plant growth.
The Adirondacks: A Gift of Wilderness
This information was compiled by the Adirondack Park Visitor Interpretive