Welcome to an extraordinary geological site hidden in plain view! At the base of Mt. Tom, overlooking the waters of Lake Bray, you’ll find an exposed outcrop of East Berlin Sandstone—an ancient record of past landscapes that tells a story of flowing water, dynamic environments, and a shifting climate from millions of years ago.
Geological Insights:
East Berlin Sandstone, a common formation in this region, is composed of very fine grains of sand that have been transported and deposited over time. As you explore this outcrop, observe the well-sorted nature of the sandstone. The grains are uniform in size, indicating they were carried over long distances by water before settling here. This fine, uniform texture is an indication of ancient riverbeds or deltas where the water flow was low and constant, allowing for the finer particles to settle evenly.
Notice the distinct, well-defined layers within the outcrop, ranging in thickness from 1mm to 10cm. These layers represent sediment deposition over time, often formed by seasonal shifts or changes in the sediment composition of the water. The beds are not perfectly parallel, which is a sign of water channels that once cut through the area. These channels would have allowed water to flow in varying directions, leading to the cross-bedding patterns and diagonal lines formed by the movement of water. The orientation of the beds indicates that the water was most likely flowing northeast. There are also small ripples that are preserved in various crevasses and surfaces of the rock, this is a direct trace of the ancient flow of water!
Geographical Context:
The East Berlin Sandstone was formed during the Triassic Period around 230 to 220 million years ago. Over millions of years, changing climates and shifting water sources led to the deposition of these sands in what was once an ancient river or delta system which drained into what was likely a much larger body of water, that has since disappeared. The geological history embedded in these rocks offers a snapshot of a time long before human civilization. This EarthCache is a journey through time, offering a unique opportunity to see evidence of ancient environments while connecting with the natural world today. Enjoy the hike, and take your time to appreciate the layers of history right beneath your feet!
To Claim the Cache, Email Me:
- A picture of a geological feature described above, either ripple marks or evidence of old water channels. Make sure that you or one of your belongings is in the picture.
- With the information above, and what you see at the site, what can you extrapolate about what the landscape looked like during the time that this rock was formed?
*Do not post pictures of the geological features mentioned here in the activity log, so that others can find them on their own. Thank you.*
Extra Credit:
- Which band inspired the title of this cache?
A note on Lake Bray:
This small lake was created in 1911 by the damming of Trout Brook and Cascade Brook.
Additional information about visiting Mt. Tom can be found here:
https://www.mass.gov/locations/mount-tom-state-reservation
To learn more about the geography of Mt. Tom check out these other Earthcaches:
Lake Hitchcock: An Introduction
Dinosaur Footprints Earthcache
Basalt Towers
References:
Professor Luce Ward’s GEO102 class at Smith College, Fall ‘24
https://mttomrange.org/bray-lake