This earthcache will bring you to Browning Mill Pond, the current home of Young Boulder, one of Thomas Dambo’s five giant wooden trolls found throughout Rhode Island’s forests and coastlines. These towering sculptures, made from recycled materials, are part of a global art project blending creativity, sustainability, and adventure. To complete this earthcache, you will need to examine the large grooved stone at the edge of the pond.
Systematic joints are regularly spaced sets of parallel or near-parallel joints, often related to tectonic stresses within the Earth's crust. They can be found in patterns, either as single sets or in multiple sets that intersect at various angles. Joints refer to fractures or cracks in rocks where there has been no significant displacement or movement along the fracture surfaces, and can occur in igneous, metamorphic, and sedimentary rocks.
Bedding planes are layers found in sedimentary rock that are distinguishable from the successive layers above and below. Each bed represents a different period of varying sedimentary deposition. Individual beds can differ from other surrounding layers in thickness, color, texture, grain size, and weathering. Cross-bedding occurs when layers of rock deposited by a flowing medium, such as wind or moving water, lie at an angle to the main horizontal bedding plane.
Glacial striations are a series of long, straight, parallel lines or grooves scratched onto a bedrock surface by rock fragments lodged in the base of a moving glacier. They are often accompanied by an extremely shiny polish left by finer grained sediments also drawn over the bedrock. Glacial striations typically form on hard rock that is relatively resistant to erosion.
Slickenlines are parallel lines or grooves commonly formed by frictional wear during sliding and movement between rock masses along a fault. They are found on smooth polished rock surfaces known as slickensides. As with glacial striations, slickenlines typically form on hard rock that is relatively resistant to erosion.
To log this earthcache, please include a picture in your log of yourself or a personal item at Browning Mill Pond and send me the answers to the following questions:
1. Examine the grooved stone. Describe the color and texture of the boulder, and compare this to the color and texture of the grooves. Are the color, texture, and direction of the grooves all consistent with the rest of the stone?
2. After reading about systematic joints, bedding planes, glacial striations, and slickenlines, which, if any, do you think is responsible for these grooves? Explain your reasoning.
Bedding and Lamination. Geology is the Way. https://geologyistheway.com/sedimentary/bedding-and-lamination/
Bhattacharya, A.R. (2022). Joints and Fractures. In: Structural Geology. Springer Textbooks in Earth Sciences, Geography and Environment. Springer, Cham. https://doi.org/10.1007/978-3-030-80795-5_13
Glacial Erosion and Deposition. SUNY OER Services. https://courses.lumenlearning.com/suny-earthscience/chapter/glacial-erosion-and-deposition/
Glacial Striations. National Park Service. https://www.nps.gov/articles/glacialstriations.htm
McCalla, C. Glacial Striations and Slickensides. Utah Geological Survey. 3 Sep 2008. https://geology.utah.gov/map-pub/survey-notes/glad-you-asked/glacial-striations-vs-slickensides/
Slickensides. USGS. 2021. https://www.usgs.gov/media/images/slickensidesjpg
Stereographic Projection of Linear Measurements. Geological Digressions. 19 Mar 2021. https://www.geological-digressions.com/stereographic-projection-of-linear-measurements/