Br🌎mide Hill EarthCache
Located at the Bromide Hill Overlook within the Chickasaw National Recreation Area, this nearly vertical 140 ft bluff overlooks the town of Sulphur and gives spectacular views of the Arbuckle Mountains and the Washita River Valley to the southwest. Local legend holds that this location was once used by early-day outlaws, hence it is also known as Robbers Roost.
To get credit for this EarthCache, be sure to complete the logging tasks at the bottom of this page.
Before We Begin:
- The Chickasaw National Recreation Area (CNRA) is open 24 hours a day, all year round except on Thanksgiving, Christmas Day and New Years Day.
- Park entrance and parking within are free.
- The CNRA attracts 1.5 million visitors a year so it can get busy at times, especially during the summer.
- If you want to visit the Travertine Nature Center, it is open 9 am to 4:30 pm daily.
- Here is a park map for your convenience.
As this is an EarthCache, there is no container to find. Instead, after you complete the two stages, you will hopefully have learned more about the following:
- How was Bromide Hill created?
- How does Rock Creek continue to shape the hill today?
Let's get started!
How was Bromide Hill created?
Let's start with a little bit of a history lesson. During the Cambrian Period (570 to 500 MYA), a large-scale faulting event formed a massive rift valley known as the Southern Oklahoma Aulacogen. During the Ordovician Period (500 to 430 MYA), the rift ceased spreading and a broad, shallow sea began to cover the entire region. For the next 200 million years, the waves of these seas rolled the sediment around creating round, smooth pebbles while marine sediments accumulated on the seafloor. The calcium-rich bodies of dead sea organisms also formed dense limestone layers, in some areas up to 2 miles thick!
During the Permian Era (280 to 225 MYA), another major geologic episode occurred and the regions' crust was greatly forced upward forming the Arbuckle Mountains. The force of this upheaval was so great that many of the sandstone, shale, and limestone layers were broken and folded, creating large anticlines (easily seen when driving along Interstate 35 in Davis, OK). During this period, these pebbles were washed down from the Arbuckle Mountains by ancient streams. Lime from these mountains eventually cemented the loose pebbles together to form a rock called conglomerate. Bromide Hill's predominant surface rock is the Vanoss Formation, consisting of this limestone conglomerate.
How does Rock Creek continue to shape the hill today?
Since the event that created the Arbuckle Mountains, the landscape of CNRA has been constantly changing through gradational processes. There are three kinds of gradational processes: weathering, gravity, and erosion. Weathering, whether it is mechanical or chemical simply prepares rock to fall or be carried away by wind or water. The gravity process refers to the force of gravity causing weathered material to transfer location. Erosion is the process by which the surface of the Earth gets worn down.
The overall process of change on the earth's surface is known as geomorphism. There are five principal geomorphic agents used to shape the land: surface water, groundwater, waves and currents, glaciers, and wind. Of these five agents, surface water and groundwater plays the most prominent role in shaping the landscape of CNRA.
Much of CNRA's landscape has evolved over the last few thousand years. Rock Creek is perhaps the dominant geomorphic feature within CNRA. This creek formed in an area that was higher than the surrounding region because of its location near the Arbuckle Uplift. Persistent runoff north and east of CNRA, along with base flow from several springs, led to the formation of Rock Creek, which cuts across the very resistant Vanoss Formation.
The creek has carved an extensive v-shaped valley through the resistant conglomerate that extends several miles and reaches depths of over 150 feet. Lateral differential erosion has widened the valley in a southward direction. This process often happens when two or more materials of differing resistance are eroded by the movement of water. The resistant Vanoss conglomerate, in this case, erodes at a slower rate than the shale and sandstone layers of the underlying Simpson Group.
Bromide Hill continues to be shaped by Rock Creek today. This undercutting action of the creek weakens rock overhangs which then fall into the creek. Remnants of one such rock fall can be found at the reference waypoint (N34 29.842 W96 59.101). Some parts of Bromide Hill are also affected by mass wasting, which results when small portions of rock and soil roll down the face of the hill into Rock Creek. Although both undercutting and mass wasting occur at a slow rate, geologists say the combined effect of these two actions will eventually lead to the leveling of Bromide Hill.
To Get Credit For This EarthCache
Copy the questions below and send your answers via geocaching messages.
- DO NOT post the answers in your log.
- Group answers are fine, just let me know who all was there.
- Note: The photo task is a requirement for each account claiming a find. See acceptable EarthCache logging tasks effective June 10th, 2019. If you don't want to post the photo with your log, you may send it to me with your answers instead.
- Please send the answers in a timely manner or it may result in the deletion of your log (no offense intended).
Logging Tasks
1| The name of this EarthCache: Br🌎mide Hill
From The Bromide Hill Overlook:
2| Provide a photo of yourself from atop Bromide Hill Overlook.
- If you prefer, it can be of a personal item instead at this location. Just make the photo unique to you and your visit. Feel free to have fun with this!
Answer the following questions:
3| Carefully look at the conglomerate rocks that form the overlook. Describe what they look like (size, shape, color). Are they loose or compact?
4| Describe evidence of erosion you see on the overlook, especially along the edge.
Optional: Carefully (and safely) peek over the edge. Do you see any evidence of previous erosion below?
Viewing Bromide Hill from Rock Creek (Stage 2 Waypoint):
5| Look at the rock wall across the creek bank. Describe what evidence you see of the effects of the gradational process here. Refer above for the different types.
6| In your opinion, do you think this creek will eventually lead to the leveling of Bromide Hill as geologist suggest?
Optional: I'd love to see other photos you took from your visit here!
*IF YOU ENJOYED THIS EARTHCACHE,
CONSIDER GIVING A FAVORITE POINT!*
Sources:
Permission for this EarthCache placement was granted by the Park Superintendent at the Chickasaw National Recreation Area.