Alaskan Muck: Gravel and Gold

In Yorkshire they say: Where there’s muck there’s brass.
In Alaska they know: Where there’s muck there’s gold.

Explanations and Excuses
In Germany the Earth Scientists have rolled up their problems into one giant aeolian spliff where everything is outa sight or blowin’ in the wind.

In the United States things are heavy for the Earth Scientists because they’re told most places were crushed under three or four kilometres of ice.

Northern hemisphere glaciation during the last ice ages.
The setup of 3 to 4 kilometer thick ice sheets

And it gets really heavy man for the over burdened Earth Scientists flying into Anchorage when they discover the high latitudes are so far out that Mother Nature only ever managed to bury half of Alaska under ice in the Ice Ages.

Because of the difficulty of correlating one isolated area in Alaska with another and the early impossibility of relating Alaskan glacial sequences to the better known glacial sequences of the north-central United States and western Europe, provincial names were given to many local Alaskan glacial chronologies established during the late 1940’s and the 1950’s.

Glaciers have covered about 50 percent of the present area of Alaska at one time or another, but large areas in central and northern Alaska have never been glaciated.

Quaternary Geology of Alaska – T L Pewe – 1975
U.S. Geological Survey Professional Paper 835

Davy Nicol performs Anchorage by Michelle Shocked

Metaphorically, Earth Science has rolled a mammoth ice-age spliff that’s liberally laced with magic aeolian dust.

The area from Long Island to Nantucket, Massachusetts was formed from glacial till, and the plethora of lakes on the Canadian Shield in northern Canada can be almost entirely attributed to the action of the ice.

As the ice retreated and the rock dust dried, winds carried the material hundreds of miles, forming beds of loess many dozens of feet thick in the Missouri Valley.

Post-glacial rebound continues to reshape the Great Lakes and other areas formerly under the weight of the ice sheets.

The Pleistocene (often colloquially referred to as the Ice Age) is the geological epoch which lasted from about 2,588,000 to 11,700 years ago, spanning the world’s most recent period of repeated glaciations.

The beauty of the ice-age spliff is that it provides an endless supply of pay-cheques for crafting magical solutions to a mythical problem.

The causes of ice ages are not fully understood for either the large-scale ice age periods or the smaller ebb and flow of glacial–interglacial periods within an ice age.

Whichever way you work it the groundhog glacial gyre is a great gravy-train.

Matanuska Glacier is a valley glacier in the US state of Alaska.

At 27 miles (43 km) long by 4 miles (6.4 km) wide, it is the largest glacier accessible by car in the United States. Its terminus feeds the Matanuska River.

It lies near the Glenn Highway about 100 miles (160 km) north-east of Anchorage. Matanuska Glacier flows about 1 foot (30 cm) per day.

And the groundhog glacial gyre sure beats a bad trip visiting reality.

But it’s not so great for those consuming the excuses, evasions, half-truths, and unsubstantiated assertions produced by the professional pundits after a few puffs of the ice-age spliff.

Alaskan Granular Material
In the realm of granular material Alaska is awesome.

Most of the low-lying areas of Alaska (except perhaps the southeastern part) are covered with either sand dunes or loess from a few millimetres to 100 m thick. Almost all these deposits are associated with glaciations.

Quaternary Geology of Alaska – T L Pewe – 1975
U.S. Geological Survey Professional Paper 835

In East-Central Alaska there are 15 flavours of granular material that include: sand, gravel, volcanic ash, loess, retransported loess, and organic deposits.

Fifteen long-recognized stratigraphic units of Quaternary age in unglaciated central Alaska are here defined and given formal names.

A systematic classification is proposed under which the Quaternary sand, gravel, volcanic ash, loess, retransported loess, and organic deposits can be readily identified.

The loess deposits and retransported loess stratigraphic units can be correlated widely in central Alaska and recognized from the Canadian border to the Bering Sea; however, the stratigraphy of underlying creek gravel deposits can be correlated only locally.

All sediments perhaps originated in a periglacial climate and are in large part perennially frozen today. The stratigraphic sequence reveals both glacial and interglacial times.

Quaternary Stratigraphic Nomenclature in Unglaciated Central Alaska
Troy L Pewe – 1975 – Geological Survey Professional Paper 862

Click to access report.pdf

Alaska has a surprising surfeit of sand.

Sand Dunes
Many of the older reports on the regional geology of areas in Alaska note the presence of active dunes, but the much larger areas of stabilized dunes commonly escaped notice.

Not until 1951 was the first small-scale map published showing the distribution of active and stabilized sand dunes, and four additional large areas of dunes have been recognized within the ensuing 10 years.

The areas of stabilized dunes are not easily recognized because they commonly are heavily vegetated, and until aerial photographs came into wide use, their distinctive form was not obvious.

Active dunes on the coastal beaches are 0.3-18 m high and consist mainly of blowout and transverse dunes, foredunes, and cliff-head dunes.

They are known mainly from the Yakutat area, the delta of the Copper River, the Bristol Bay area, Seward Peninsula, and northern Alaska but are present everywhere on sandy coasts.

The two largest areas of active dunes in Alaska are not, however, along modern beaches but are in the Koyukuk and Kobuk River valleys.

The active Nogahabara dune field in the lower valley of the Koyukuk is only a small part of a much larger Pleistocene dune field that is now mostly inactive.

The active dune area is approximately 65 km2 and is composed mainly of transverse dunes 15-60 m high and 90 m long or more.

The middle Kobuk valley contains another large area of Pleistocene dunes, of which 130 km2 contains active dunes.

Stabilized dunes, probably of Illinoian and Wisconsinan age, are widespread, especially in central and northern Alaska, but only locally have they been mapped in even a reconnaissance fashion.

Most of the dunes occur in the valleys of the Tanana, Yukon, Kuskokwim, Koyukuk, and Kobuk Rivers-rivers that were important streams draining glaciated areas in the past.

Quaternary Geology of Alaska – T L Pewe – 1975
U.S. Geological Survey Professional Paper 835

Carcross Desert, located outside Carcross, Yukon, Canada, is often considered the smallest desert in the world… measures approximately 1 square mile…

The sand was formed during the last glacial period, when large glacial lakes formed and deposited silt. When the lakes dried, the dunes were left behind


Alaska is really loaded with loess.

Loess probably is the most widely distributed sediment of Quaternary age in Alaska. It forms a blanket, ranging in thickness from a few millimetres to more than 60 m, that covers almost all areas that lie below altitudes of 300-450 m.

Thick deposits of loess are most widely distributed in central and western Alaska. Most of the loess was deposited during Illinoian and Wisconsinan time, but wind-blown silt is still being deposited in many areas.

The loess is of great economic importance because it forms the soils of the principal agricultural areas in Alaska.

The wind-blown silt of Alaska was first described by Spurr, who applied the name “Yukon silts” to deposits in the valleys of the Yukon River and its tributaries.

For nearly 50 years, the origin of these silts was a matter of controversy; various workers argued for a fluvial origin, a lacustrine origin, a marine and estuarine origin, or a residual origin. Although Tuck and Eardley correctly recognized that most of the silt was of wind-blown origin and Capps referred to eolian origin, Taber argued that the silt, including the reworked valley-bottom silt rich in organic material, was entirely the product of prolonged disintegration of local bedrock by frost riving.

The writer, however, showed that the thick silt deposits of the Fairbanks district are of eolian origin, and Trainer and Hopkins confirmed the eolian origin of surficial silt blankets in the Matanuska Valley and central Seward Peninsula.

The thick deposits of valley bottom loess are called muck.

The loess of Alaska was blown from the vegetation-free flood plains of braided glacial rivers; consequently, loess is thickest near streams draining glaciated areas.

At the present time, loess is being deposited most rapidly near the modern outwash streams.

Loess has been deposited on ridges as high as 760 m above sea level, but most seems to have been deposited at altitudes of less than 450 m.

A large part of the loess falling on summits and slopes of hills has been washed into valley bottoms to form thick deposits of bedded to massive silt that is rich in organic debris.

These deposits locally are called muck.

The bedded character of the valley-bottom silt has been used as evidence to support hypotheses for the marine, lacustrine, and residual origin of loess.

The loess in Alaska is similar in texture and color to loess elsewhere in the world.

Typically, 80-90 percent of the particles are between 0.5 and 0.005 mm in size.

Particle size increases with decreasing distance from the river flood plains that constitute the source areas.

Colors range from chocolate brown through tan to olive gray and neutral gray.

Mineral and chemical composition reflect differences in bedrock composition of the
glaciated valleys from which the particles were ultimately derived.

Loess typically contains minerals that are not present in the bedrock of areas where it was
deposited by the wind.

The thickest loess known in Alaska is north of the Tanana River near Fairbanks, where a blanket 61 m thick covers the top of Gold Hill.

Greater thicknesses of silty sediments (as much as 95 m) occur in the bottoms and lower slopes of small valleys in the Fairbanks area, but these represent deposits reworked from adjoining slopes.

Deposits 3-12 m thick occur along the entire north side of the Tanana valley and on both sides and in the middle of the lower Yukon River valley.

Loess is thick adjacent to the Yukon Flats and the upper Kuskokwim valley.

Many metres of wind-blown silt exist along the central Copper and lower Chitina valleys and near Palmer.

Loess more than 1.5 m thick covers about three-quarters of the area of Seward Peninsula.

The major river valleys on the Arctic Slope are flanked by loess that is generally many metres thick, but the loess blanket thins considerably immediately away from the rivers.

Quaternary Geology of Alaska – T L Pewe – 1975
U.S. Geological Survey Professional Paper 835

And below the muck are gravels containing gold.

Auriferous Gravel of Central Alaska
Perhaps the most famous of the fluvial deposits of Alaska and adjoining Yukon Territory, Canada, are the late Tertiary(?) to middle Quaternary auriferous creek and river gravels now buried by frozen silt or other sediments.

These gravel deposits are almost entirely confined to unglaciated central Alaska and, in most instances, are buried by retransported loess.

Quaternary Geology of Alaska – T L Pewe – 1975
U.S. Geological Survey Professional Paper 835

Miners have gone to extraordinary lengths to get at the golden gravel.

The typical Alaska “muck” is described by Mertie’ as a dark gray to black silt, principally derived from the underlying schist bedrock, containing a considerable quantity of vegetal material, lenses of ice, and strata of peat and volcanic ash.

These silt or muck deposits are eternally frozen three feet below the surface.

Tuck differentiates between silt and muck pointing out that the silt occurs only on the sides of the valleys and is unfrozen.

Many of the local miners refer to these side valley deposits as “dry muck.”

The muck blankets considerable portions of the interior of Alaska in thicknesses varying from four or five feet to over 100 feet in the vicinity of Fairbanks.

These muck deposits and accompanying sedimentary depositions are regarded as late Pleistocene or Early Recent in date and overlie older Quaternary gravels.

In the streams and valleys of the Yukon and its tributaries, most of the placer gold mining operations are carried on in these older gravels.

The superimposed muck, with its frozen bulk, must first be removed, consequently to expose the auriferous gravels beneath.

It is in these placer operations, for the most part of a hydraulic nature, that most of the information of the muck deposits is to be gleaned.

Archaeological Aspects of the Alaska Muck Deposits – Frank C Hibben – 1941
New Mexico Anthropologist, Volume 5, Number 4

Russian explorers discovered placer gold in the Kenai River in 1848, but no gold was produced.

Gold mining started in 1870 from placers southeast of Juneau, Alaska.

Gold is found and has been mined throughout Alaska; except in the vast swamps of the Yukon Flats, and along the North Slope between the Brooks Range and the Beaufort Sea.

Areas near Fairbanks and Juneau, and Nome are responsible for most of Alaska’s historical and all current gold production.

The largest gold producer is the Fort Knox mine, a large open pit and cyanide leaching operation in the Fairbanks mining district. Fort Knox produced 401,553 troy ounces (12,489.7 kg) of gold in 2015.

And in the process they’ve encountered some extraordinary items…

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12 Responses to Alaskan Muck: Gravel and Gold

  1. Aolean origin – Tuffs and other volcanogenic silts/sands could also be described as aeolian deposits since these are also deposited from the atmopshere. Source? The various maars and related volcanic diatremes in Alaska?

    • malagabay says:

      Once again you’re right on target with [for starters] four of the largest maars on Earth.

      The Espenberg Maars consist of four large, separate eruptive craters, each excavated 100 – 300 m into Pleistocene sediments and lavas.

      Devil Mountain Lakes Maar on the northern Seward Peninsula is the largest known maar on earth, and South Killeak, North Killeak, and Whitefish Maars are also larger than any previously described maars on earth.

      The Espenberg Maars were formed by highly explosive hydromagmatic eruptions through permafrost.

      The Largest Known Maars on Earth, Seward Peninsula, Northwest Alaska
      James E. Begét, David M. Hopkins and Steven D. Charron
      Arctic – Vol. 49, No. 1 – Mar., 1996

      Click to access Arctic49-1-62.pdf

      Devil Mountain Lakes is a maar (a form of crater lake) in the western part of Alaska. The lake is considered to be the largest maar in the world.

      The crater lake has a diameter of about 8 kilometers (5.0 mi) and is part of the Bering Land Bridge National Preserve. Devil Mountain Lakes are rather unusual consisting of a double crater divided into North Devil Mountain lake having a diameter of about 5.1 km (3.2 mi) and South Devil Mountain lake having a diameter of about 3.4 km (2.1 mi).

      66°23′58″N 164°29′12″W

    • malagabay says:


      Seward Peninsula looks like it’s a pivot point.

      Friction would be a source of heat if the surface is sliding about.

      More details in the next post to follow…

    • malagabay says:

      Nunivak Island is a permafrost-covered volcanic island lying about 30 miles (48 km) offshore from the delta of the Yukon and Kuskokwim rivers in the US state of Alaska, at a latitude of about 60° N.

      It is 76.2 kilometers (47.3 mi) long and 106 kilometers (66 mi) wide.

      Nunivak Island is volcanic in origin; most of the island is dominated by volcanic plateau 500 ft (160 m) or more above sea level.

      The island is dotted with about 60 cinder cones and four maars.

      Much of its surface consists of widespread, thin flows of pahoehoe lava from small shield volcanoes, which spread over sedimentary rock of the Cretaceous period.

      Volcanic eruptions took place during 5 periods of activity beginning 6.1 million years ago.

      Most of the volcanic field was formed during the two most recent eruptive periods during the Pleistocene ending about 300,000 years ago.

    • malagabay says:

      The St. Michael volcanic field is a volcanic field located on St. Michael and Stuart Islands in western Alaska, United States. It contains 55 cones and craters, including low broad shield volcanoes and maars.

      The oldest Eskimo settlements in Western Alaska date to around 200-500 BC, so mountains in the St. Michael volcanic field likely erupted sometime within the last 3,000 years.

    • malagabay says:

      The Ukinrek Maars are two phreatomagmatic vents that formed on the north side of the Aleutian Range on a low area bordering the Bering Sea.

      The maars are 1.5 km south of Becharof Lake and 12 km northwest of Peulik Volcano.

      The western of the two is elliptical in shape and up to 170 m in diameter and 35 m deep.

      The east maar lies 600 m to the east and is circular and up to 300 m in diameter and 70 m deep.

      The east maar has a 49 m-high lava dome within the crater lake.

      The eruption occurred in March and April 1977 and lasted for ten days.

  2. THX1138 says:

    Sock it to ’em, man.

  3. Re Seward peninsula:

    If the Electric Earth model by Michael Csuzdi is used, the MOHO is interpreted as a proton rich layer underlying negative charged crust. If an exogenous positively charged plasma vortex decends from the ionosphere impacting the Earth, water saturared etc,, and continues to “screw” downwards into the crust towards the MOHO, then this additional positive charge might spread out laterally under the crust as sheet lightning and then allow the crust to “float” over the MOHO, inter alia. Csuzdi believed that continental drift was powered by electric charge.

  4. Sheila Hendry says:

    “And in the process they’ve encountered some extraordinary items……”
    Don’t stop there 🙂

  5. Pingback: Alaskan Muck: The Swing State | MalagaBay

  6. Pingback: Alaskan Muck: The Missing Ice Age | MalagaBay

  7. Pingback: Alaskan Muck: Alaskan Ash | MalagaBay

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