Daily Dose of Happiness US # 66 – Ozark Rock Layers
Take a look at the rock exposure in front of you. You are looking at a small piece of the geologic story of the Missouri Ozarks.
The rocks here began as layers of sediment deposited long ago. In the Ozarks, much of the bedrock was formed from sediments deposited in ancient seas that once covered this region. Over time, those sediments were buried, compacted, and cemented together to form sedimentary rock. Since then, the rock has been fractured, weathered, and eroded.
The result is the rock exposure you see today, where some layers stand out as ledges while other material has worn away. This type of exposed bedrock and uneven landscape is common throughout the Missouri Ozarks.
The rocks may look quiet and ordinary, but they record a very long history.
Earth Science Concepts Demonstrated
- Sedimentary rock
- Deposition
- Lithification
- Weathering and erosion
- Resistant and less-resistant rock
- Ledge formation
- Missouri Ozarks geology
Look closely at the rock exposure. The rock you see is sedimentary rock. Long ago, sediment was deposited in layers. As additional sediment accumulated, the older layers were buried beneath younger ones.
With increasing burial, pressure and naturally occurring minerals helped compact and cement the sediment together. This process is called lithification, turning loose sediment into solid rock.
The layers did not remain unchanged.
Over time, the rock developed cracks and fractures. Water could enter some of these openings, allowing weathering to work on the rock. In the Ozarks, water has played an important role in shaping the landscape and exposing the bedrock we see today.
Weathering breaks rock down, while erosion removes the loosened material. These processes do not affect every layer at the same rate. Some layers are harder and more resistant, while others break down more easily.
That difference in resistance is what helps create the ledges and uneven profile you can see in the exposure today.
So look at the rock again.
The different layers are not just stripes in the rock. Each layer represents sediment deposited at a particular time in Missouri's geologic past. The cracks, weathering, and ledges are evidence of what happened to those layers long after they were deposited.
This small exposure is just one example of the geology that helps give the Missouri Ozarks its distinctive rocky hills, bluffs, valleys, and outcrops.
You are literally looking at layers of time in the Ozarks.
Logging Tasks Required:
To earn credit for this Earthcache, please answer all the following questions based on information on this cache page and on your observations at the posted coordinates. Please send your responses to the cache owner via the Geocaching.com message center or email. All reasonable observations/answers will be accepted.
1. Look closely at the exposed rock. How many distinct layers or bands can you identify?
2. Do the layers all look alike? Describe at least one difference you can see between two or more layers, such as colour, thickness, texture, or how they weather.
3. Examine the cracks and fractures in the exposed rock. Are they mostly horizontal, mostly vertical, or do they run in several directions?
4. Which layers appear to be the most resistant to weathering? What do you see that makes you think so?
5. Look at the shape of the rock exposure. How has the difference between harder and softer layers helped create the ledges you see today?
6. Required Photo: Post a photo with your log showing yourself (you do not have to show your face), a personal item, your pet, or your GPS/device with the rock formation in the background.
Please do not reveal the answers in your photo or log text.
Resources
U.S. Geological Survey – Geology https://www.usgs.gov/programs/geology
National Park Service – Geology https://www.nps.gov/subjects/geology/
Encyclopaedia Britannica – Sedimentary Rock https://www.britannica.com/science/sedimentary-rock
