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America's Volcanic Past
North Dakota

"Though few people in the United States may actually experience an erupting volcano, the evidence for earlier volcanism is preserved in many rocks of North America. Features seen in volcanic rocks only hours old are also present in ancient volcanic rocks, both at the surface and buried beneath younger deposits." -- Excerpt from: Brantley, 1994
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Map, Location of North Dakota

Volcanic Highlights and Features:
[NOTE: This list is just a sample of various North Dakota features or events and is by no means inclusive. All information presented here was gathered from other online websites and each excerpt is attributed back to the original source. Please use those sources in referencing any information on this webpage, and please visit those websites for more information on the Geology of North Dakota.]

  • North Dakota
  • North Dakota Regions
  • Badlands
  • Killdeer Mountains
  • Little Missouri Badlands
  • Theodore Roosevelt National Park
  • Volcanic Ash and Tuffs

North Dakota

North Dakota lies within the Interior Plains, that vast region stretching from the Rocky Mountains to the Appalachians. In North Dakota, the Interior Plains are divided into two major physiographic provinces by the Missouri Escarpment. To the north and east of the escarpment lies the Central Lowlands Province, characterized by its glacially smoothed landscape. To the south and west, the Great Plains Province rises gradually westward toward the Rocky Mountains. White Butte, at 3,506 feet above sea level in the southwestern corner of the state, is the highest point in North Dakota. The lowest point in the state is 750 feet above sea level, where the Red River crosses into Manitoba. At its most basic then, North Dakota forms a gentle plain that slopes northeast. But this surface is greatly modified by landforms created by glacial ice, glacial lakes, and catastrophic floods of glacial meltwater, as well as by the relentless erosion by water and wind that created the buttes and badlands of the southwestern part of the state. Through the eyes of a geologist, the North Dakota landscape is tremendously varied, ranging from exceptionally flat plains of glacial lakes to rugged badlands.


Excerpt from: John Bluemle and Bob Biek, No Ordinary Plain: North Dakota's Physiography and Landforms, North Dakota Notes No.1, North Dakota Geological Survey Website, July 2001

   
North Dakota Regions

The Interior Plains:3
The Interior Plains is a vast region that spreads across the stable core (craton) of North America. This area had formed when several small continents collided and welded together well over a billion years ago, during the Precambrian. Precambrian metamorphic and igneous rocks now form the basement of the Interior Plains and make up the stable nucleus of North America. With the exception of the Black Hills of South Dakota, the entire region has low relief, reflecting more than 500 million years of relative tectonic stability.

North Dakota and the Interior Plains:1
North Dakota lies within the Interior Plains. In North Dakota, the Interior Plains are divided into two major physiographic provinces by the Missouri Escarpment. To the north and east of the escarpment lies the Central Lowlands Province, characterized by its glacially smoothed landscape. To the south and west, the Great Plains Province rises gradually westward toward the Rocky Mountains.


   

Badlands

North Dakota Badlands:2
About 60 million years ago, streams carried eroded materials eastward from the young Rocky Mountains and deposited them on a vast lowland -- today's Great Plains. During the warm, rainy periods that followed, dense vegetation grew, fell into swamp areas, and was later buried by new layers of sediments. Eventually this plant material turned into lignite coal. Some plantlife became petrified; today considerable amounts of petrified wood are exposed in the badlands. Bentonite, the blue-gray layer of clay, may be traced to ash from ancient volcanoes far to the west. But even as sediments were being deposited, streams were starting to cut down through the soft strata and to sculpt the infinite variety of buttes, tablelands, and valleys that made up the badlands we know today.

Bentonite Clay:2
The story of the badlands begins over 65 million years ago during the Paleocene Epoch. The dinosaurs had just become extinct at the end of the Cretaceous Period. The western half of North America was buckling and folding to create the Rocky Mountains. Large amounts of sediments were forming as water, wind, and freezing worked to break down the mountains. These sediments, mostly sand, silt, and mud, were carried off the eastern slopes by ancient rivers and deposited here in layers. Volcanoes in South Dakota, Montana, Idaho, and across the west were also erupting during this time, spitting out huge amounts of ash. Some of this volcanic ash was blown or carried by rivers into North Dakota and accumulated in standing water. Over time, the sediments turned into the sandstone, siltstone, and mudstone layers now exposed in the park, while the ash layers became bentonite clay.




Killdeer Mountains

Killdeer Mountains:1
The buttes that make up the Killdeer Mountains are erosional outliers, probably places where large lakes in which sandy and limy sediments and some stream deposits accumulated in middle to late Cenozoic time. Repeated volcanic eruptions in the Rocky Mountains to the west produced large amounts of ash, which blew eastward, fell to the ground, and washed into the lakes, forming tuffaceous (meaning they contain volcanic ash) sandstones. About 5 million years ago, long after the lakes were filled, a new erosional cycle began. The relatively hard tuffs and freshwater limestones and sandstones that had been deposited in the Miocene lakes were much more resistant to erosion than were the surrounding sediments. Because of their resistance to erosion, these hard materials remained standing above the surrounding area as the softer Golden Valley and Sentinel Butte sediments were eroded and carried away by streams and rivers to Hudson Bay. The Killdeer Mountains, with their resistant caprock, are the result of that erosion cycle; they are the modern manifestation of an ancient lake bed.

Arikaree Caprock:1
The Arikaree caprock of the Killdeer Mountains consists of tuffaceous sandstone and siltstone that is interbedded with thin layers of freshwater carbonates. Dating techniques performed a tuffaceous layer 200 feet below the top of South Killdeer Mountain indicated that volcanic ash at that horizon was deposited approximately 25 million years ago. The presence of interbedded carbonates in the tuff would make mining and processing of this material very difficult. The tuffaceous rocks are present throughout the 4,800 acre area of the Killdeer Mountains.




Little Missouri Badlands

Weathered Volcanic Ash Marker Beds:1
The most widespread and spectacular badlands in North Dakota border the Little Missouri River, northward from the headwaters area in Wyoming, where they are developed in rocks as old as Cretaceous, to the point where the river flows into the Missouri River. Some exposures in the northern part of the Little Missouri Badlands are eroded from beds as young as Eocene age, but most of the area of the badlands along the Little Missouri River is carved from the Bullion Creek and Sentinel Butte formations, both of Paleocene age. The sedimentary layers exposed in the Little Missouri Badlands are mainly continental sediments that were deposited by rivers and streams flowing east to the Dakotas from the Rocky Mountains in Montana and Wyoming at the time of the Laramide orogeny. They consist of layers of poorly lithified siltstone, claystone, sandstone, and lignite coal that were deposited in a coastal plain environment. River, floodplain, and swamp deposits predominate. Bluish gray layers of weathered volcanic ash form excellent marker beds in places and brownish gray layers of sand containing thin, orange, iron-rich bands also form prominent markers. Black veins of lignite coal are common and reddish bands of clinker (materials that were baked when buried lignite veins burned) add color to the area.




Theodore Roosevelt National Park

Theodore Roosevelt National Park:1
Theodore Roosevelt National Park consists of a North Unit, near Watford City (McKenzie County) and a South Unit, near Medora (Billings County). Between the two units, 70,228 acres (about 110 square miles) of land are included in the park boundaries. The badlands of Theodore Roosevelt National Park, formed mainly through erosion by the Little Missouri River, have attracted geological interest since the days of the early scientific explorers primarily because of the well exposed rock formations and the scenic beauty of the area. Two primary rock formations are exposed in the park, the Bullion Creek Formation and the overlying Sentinel Butte Formation. A widespread ash/bentonite deposit called Sentinel Butte ash, at times 25 feet thick, occurs in the Sentinel Butte Formation in the North Unit.

Sentinel Butte Bentonite:1
During the Laramide, volcanoes erupting to the west spewed ash that was carried by the wind to western North Dakota where it washed into wet areas - lakes and lagoons. With the passage of time the ash was transformed to bluish, bentonite clay layers that can be seen today in the badlands areas. Bentonite is composed principally of the clay mineral montmorillonite, which if it contains sodium as an exchangeable ion, can swell conspicuously when wet; calcium bentonites are only slightly swelling or non-swelling. The Sentinel Butte bentonite is an iron- and sodium-rich montmorillonite, one of three major Paleocene-age bentonites in North Dakota shown to have been derived from volcanic ash. The bentonites in the badlands can absorb up to several times their weight in water and they are extremely slick and mobile when wet. They form a characteristic popcorn-like surface when dry.




Volcanic Ash and Tuffs

Volcanic Ash and Tuffs:1
Several volcanic ash beds or tuffs are known to be present in western and central North Dakota. These tuffs range in age from 70 to 20 million years and are believed to have originated from volcanoes in south-central and western Montana and northern Wyoming. Numerous additional volcanic ash beds are likely present in the Pierre and Niobrara formations but most, if not all, of the glass shards have been altered to bentonitic clay. These tuffs generally are thought to be the result of single or related airfall events that likely deposited a rather thin layer of volcanic dust across a wide area. In turn this volcanic dust was transported by wind and rain into streams and redeposited in local basins, commonly lakes, as thick tuffs. As a result of this reworking, an inch or less of volcanic dust may result in 20 feet or more of tuff. The glass grains or shards in tuffs have been used in the manufacture of road base construction, concrete admixtures and aggregates, abrasives, cleansers, polishing compounds, slow release fertilizers, ceramics, absorptives, and fillers. Tuffs have been discovered in Emmons, Sioux, Stark, Dunn, Slope, and McKenzie counties. The most well known tuff deposit is the Linton Ash which has been actively promoted for a period of twenty years but has undergone little development.

Antelope Creek Ash:1
A 2-to 3 foot tuff layer (Antelope Creek Ash) is present in the lower portion of the Brule Formation in the Little Badlands southwest of Dickinson. This tuff is very fine grained and initial attempts at dating this layer failed. The Antelope Creek Ash may extend over an area of 2000 acres.

Arikaree Caprock:1
The Arikaree caprock of the Killdeer Mountains consists of tuffaceous sandstone and siltstone that is interbedded with thin layers of freshwater carbonates. Dating techniques performed a tuffaceous layer 200 feet below the top of South Killdeer Mountain indicated that volcanic ash at that horizon was deposited approximately 25 million years ago. The presence of interbedded carbonates in the tuff would make mining and processing of this material very difficult. The tuffaceous rocks are present throughout the 4,800 acre area of the Killdeer Mountains.

Linton Ash:1
The Linton Ash is well exposed in the hills north of the town of Linton in Emmons County. The Linton Ash occurs in the lower part of the Fox Hills Formation and consists of 25 feet of fine grained, moderately indurated tuff. There is approximately 500 million tons of ash in a 4,000 acre area around Linton.

Marmarth Ash:1
The Marmarth Ash, is present in the uppermost part of the Hell Creek Formation northeast of the town of Marmarth in Slope County. The Marmarth Ash consists of approximately 6 feet of unaltered (white) tuff which is bounded by bentonite (gray). The bentonite was formed by the alteration of the volcanic glass. This tuff could only be traced through portions of two sections indicating it may only extend over an area of 600 acres.

Sentinel Butte Tuff:1
The Sentinel Butte tuff or blue bed occurs near the middle of the Sentinel Butte Formation in McKenzie County. The Sentinel Butte tuff is best exposed in the North Unit of the Theodore Roosevelt National Park and extends to the northern edge of McKenzie County, an area of at least 600 square miles. The Sentinel Butte tuff is up to 23 feet thick commonly comprised of an unaltered tuff layer ranging in thickness from 0 to 6 feet which is bounded by bentonite layers that range up to 12 feet thick.


Excerpts from:
1) North Dakota Geological Survey Website, July 2001
2) U.S. National Park Service, Theodore Roosevelt National Park Website, 2002
3) USGS/NPS Geology in the Parks Website, August 2001

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01/28/03, Lyn Topinka