America's Volcanic Past -
Kansas

The Earth is billions of years old. In Kansas, hills were formed that were later buried or worn away by wind and water. Seas covered parts of the state, then disappeared. Giant sheets of ice called glaciers moved into northeast Kansas, then melted. Rivers changed their courses. The climate changed -- sometimes hot, sometimes cold, sometimes wet, sometimes dry. These changes are what made Kansas look the way it does today.

Igneous rocks are formed when a hot liquid, called magma, cools and changes from a liquid state to a solid state. They may form slowly underground or rapidly at the Earth's surface. When magma reaches the surface, it is called lava. Lava flows out of a volcano and quickly hardens after an eruption. Although most lava reaches the surface through volcanoes, it may also flow out of deep cracks in the earth without building a mountain.

Kansas doesn't have an active volcano, but lava did flow onto the surface as recently as 90 million years ago when dinosaurs still roamed the Earth. Hot magma forced its way up from over 100 miles below the Earth's surface in two small areas of eastern Kansas. The hot liquid, which spread upward through cracks in other underground rocks, cooled and hardened, forming a rock called lamproite in Woodson and Wilson counties and one called kimberlite in Riley County.

In one area of Riley County, lava flowed onto the surface but a volcanic cone was never formed. The kimberlite formed from the lava is now buried. Lamproite and kimberlite found at the surface in Kansas were exposed when the rock above was eroded away. Diamonds have been found in kimberlites and lamproites in other parts of the world, but none has been found yet in Kansas.

Granite, another type of igneous rock, has been found mixed with lamproite in Woodson County. It is older than the surrounding surface rocks and was formed deep in the Earth. Lamproite magma carried it toward the surface, where it is now exposed.

Some igneous and metamorphic rocks have traveled into Kansas from other places. Volcanic ash, basalt, granite, and quartzite have been carried in by wind, glaciers, and water.


Excerpts from: Kansas Geological Survey Website, 2001

The Interior Plains:²
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.

Precambrian:¹
These rocks are the oldest on earth. In Kansas, they are only found deep below the surface and not much is know about them. Many are igneous and metamorphic and have gone through many changes.

Midcontinent Rift:³
The 1,100 million-year-old Midcontinent rift system extends north-northeast from Kansas for about 2,000 kilometers to Lake Superior, and then southeast through Michigan. The rift is almost completely buried beneath a cover of Paleozoic and younger sedimentary strata; its position has been deduced from gravity and magnetic anomalies. However, significant exposures of rift-related rocks do occur around the margin of Lake Superior. There, surface rocks are a bimodal suite of mostly tholeiitic basalt and some alkaline basalt along with minor silicic rocks. The alkaline rocks are more abundant in the lower part of the stratigraphic sequence whereas tholeiitic rocks become more abundant up-section. U-Pb zircon dating of basal volcanic rocks and related sills around the shores of Lake Superior imply that rift-related magmatism began about 1,108.8 + 4/-2 million years ago during a period of reversed magnetic polarity. The magnetic polarity shifted back to normal between 1,097.6 ± 8.7 million years ago and 1,086.5 + 1.3/- 3.0 million years ago. Although volcanism was active in the Lake Superior region for about 22 million years, most of the activity was restricted to the 3 to 5 million years interval shortly after 1,097 million years. Very few drill holes penetrate the rift-related rocks south and west of Lake Superior; however, several sampled volcanic sequences in southern Kansas have chemical characteristics similar to those associated with the rocks exposed around Lake Superior. The basaltic sequence in Kansas is subalkalic to alkalic and follows tholeiitic trends: a number of individual flows of high-alumina basalt are scattered throughout the sequence.

Next 500 plus million years:¹
Seas came and went.

Quaternary (last 1.6 million years):¹
Early, the land was stable with some erosion. Glaciers moved into the northeast at least twice. Later the climate was dry. Sand dunes were formed by wind in the west. Volcanic ash was blown in from California, New Mexico, and Wyoming.

Cretaceous Igneous Rocks:
Kimberlite (Riley County); Rose Dome Lamproite (Woodson County); Silver City Dome Lamproite (Woodson County)

Kansas's Interior Plains Region:¹
The Kansas landscape was formed by alternating periods of deposition and erosion. This landscape divides regions of Kansas according to physical geology, or physiography. Each region is different, and that difference is determined largely by geology, along with other factors such as climate.

Kansas's Ozark Plateau:¹
The Ozark Plateau in extreme southeastern Kansas is made up of rocks deposited during the Mississippian Period of geologic history, about 350 million years ago. During the Mississippian, repeated layers of limestone, shale, and sandstone indicate that seas rose and fell. Mississippian rocks are the oldest found at the surface and are in the southeast corner; elsewhere these rocks are only underground.

Kansas's Cherokee Lowlands, Osage Cuestas, and Chautauqua Hills:¹
Landforms in the Cherokee Lowlands, Osage Cuestas and the Chautauqua Hills are all Pennsylvanian in age, deposited about 300 million years ago. For much of the period the land was flat. Seas and swamps came and went; coal formed in swamps from dead plants. Shale, limestone, sandstone, chert, and conglomerates were deposited. Two ridges of hills, the Nemaha uplift and the Central Kansas uplift, appeared; both are now buried. Pennsylvanian rocks are found at the surface in eastern Kansas.

Kansas's Flint Hills and Red Hills:¹
The Flint Hills of east-central Kansas and the Red Hills in the south-central part of the state are both Permian in age, roughly 250 million years old. During the Permian much of Kansas was covered by several seas. As they rose and fell, limestone, shale, and chert were deposited. The Flint Hills formed. When the seas dried up, salt and gypsum were left behind. The Red Hills were formed from deposits of shale, siltstone, gypsum, and dolomite.

Kansas's Smoky Hills:¹
Cretaceous-age rocks, deposited about 100 million years ago during the time of the dinosaurs, form the landscape in the Smoky Hills. During the Cretaceous, much of the western half of Kansas was covered by seas. Limestone, sandstone, and chalk formed from sea deposits. Fossils can be found in these rocks, which crop out in central and western Kansas.

Kansas's High Plains:
The High Plains of western Kansas are composed of rock debris washed off the face of the Rocky Mountains over the past few million years.

Kansas's Arkansas River Lowlands and Wellington-McPherson Lowlands:¹
The Arkansas River Lowlands and the Wellington-McPherson Lowlands are areas of recent deposition that border rivers.

Kansas's Glaciated Region:¹
Glaciers moved into Kansas about 750,000 years ago and sculpted the northeastern corner of the state.