Texas Blackland Prairie: The Flower Mound EarthCache

Welcome to The Flower Mound, the natural site that influenced the name of the surrounding town: Flower Mound. This name was originally derived from remarks made by settlers from the 1800’s who noticed an abundance of various wildflower species that grew there. In 1892, a town resident named Otto Consolvo decided to dedicate his life to protecting the area from growing property development, and in the summer of 1893, he and many other residents purchased the site and turned it into a land conservancy, eventually becoming an official Texas Historic Site in 1984. Many years later, this landform still stays true to it’s name, serving as a habitat for bluebonnets, wild foxglove, field pansies, Indian blankets, prairie grounsels, and more wildflowers, including various types of grasses. 

Before we get into the geological history of the Mound, it is important that we cover the various ways mounds, or hills, can form. The most common methods are: 

Fault Formation- Faults are areas in the Earth where there is a displacement of rock movement. These are often created by tectonic plate movement, such as the subduction of one or more plates under another, or the sliding of two plates across each other. When faults raise upwards above ground, they are able to form hills.

Landform Erosion and Deposition- Hills are sometimes formed by the erosion of other landforms, in particular, Mountains. Mountain erosion often occurs from wind, however other methods such as water are also possible. Once these sediments are carried away, they may pack into a certain area, eventually forming a hill.

Glaciers- Glaciers often deposit sediments from higher elevations, forming uniquely shaped hills.

Volcanic Activity- Once volcanoes erupt, they send lava flowing out, with ash following. When the ash hits the lava, it stays put until rain pours into the mixture, creating black water. The black water eventually hardens and cracks and crumbles into a hill.

Artificial- Manmade hills are sometimes created for recreational use, or for help in restoring once-existing environments.

Combinations of the above methods are also possible in hill formation. There are also different types of hills. The most common types are:

Brae- Steep hillside often found alongside a river.

Drumlin- A small hill that is often a member of a group of similar hills made up of compacted boulder clay molded by past glacial action.

Butte- An isolated hill with steep sides and a small flat top that is formed by weathering.

Kuppe- A hill with a rounded summit that has no major rock formation on top.

Tor- A hill with a very rocky hilltop.

Puy- A conical volcanic hill.

Pingo- A collection of earth-covered ice often found in the Arctic/Antarctica.

With hill background information now covered, we can get into the geological history of this Mound:

In the Late Cretaceous Period 80-118 million years ago, warmer climate influenced from the Late Jurassic/Early Cretaceous resulted in drastic sea level rise, creating many inland seas. In North America, the colliding of the Kula and Farallon tectonic plates with the North American tectonic plate created an opening in the Arctic Ocean and the Gulf Of Mexico for seawater to travel through, submerging the majority of modern day Texas, Colorado, New Mexico, Nebraska, The Dekotas, Minnesota, Wyoming, Montana, Midwest Canada, Eastern Mexico, and parts of Louisiana, New Mexico, Utah, and multiple other states. This newly formed sea was called the Western Interior Seaway and stretched over 2,000 miles long, 620 miles wide, and up to 3,000 ft deep (shallow in relation to other Seaways at the time). This massive Seaway split North America into two seperate land masses: Westerm Laramidia, and Eastern Appalachia. While the Kula and Farallon plates subducted beneath the North American plate, multiple hills and mountains slowly began to form, helping to create the basis for landforms such as the Mound that we have today. Sediments from areas above water were slowly weathered and eroded away, eventually joining these forming features. 

At around 70-80 million years ago, the continuous subduction of the Kula and Farallon under the North American plate created the great Laramide orogeny, a very important period of mountain formation that occurred towards the end of the Cretaceous period. The shallow angle subduction of the Farallon ended up creating the early stages of the Rocky Mountains, and overtime the orogeny sped up, raising the lagoons and sandbanks of the Seaway. The Western Interior Seaway would soon divide between the Dakotas, and retreat back down to Texas, creating a larger Gulf of Mexico. The regression of the Western Interior Seaway would form the short-lasting Pierre Seaway, before leaving the majority of the North American continent. It was at around this time that the Cretaceous would end and the Paleogene would begin, some 66 million years ago. The Earth began to cool, and the Pierre Seaway disappeared, leaving this part of Texas behind with a Mound amid the newly-formed Blackland Prairie. The Mound would become a noticeable landmark due to it’s height (50-60 feet) above the surrounding prairie, and many new species of plants would soon spread to the area, bringing various fauna along with them.

Years later, The Flower Mound would become a popular resting and surveying point for early American settlers traveling through the area. Nearby Native American tribes would cross through the prairie, possibly following the wild buffalo herds, and often use the base of the hill as a camp spot, as hinted at by pottery fragments found around the area in the 1970’s. Unfortunately, the majority of the surrounding Blackland Prairie would be taken up by new forests and eventually urban development, but thanks to conservation efforts, the Mound still stands as the largest area of untouched Blackland Prairie land!