Sidewalk Geology Background Information The roads and sidewalks near our homes are filled with interesting and exciting geological discoveries to be made! Most sidewalks and roads are composed of aggregate (small pieces of material like sand, gravel, crushed stone, etc.) mixed into a base material. Aggregate adds strength to the larger medium and gives our roads and sidewalks their various colors and textures. Most aggregate in the Twin Cities area is gravel consisting of quartz-based rocks, like granite. You can also find a fair amount of sandstone, limestone, and basalt. These rocks are typically harvested from streams and riverbeds. Because of the wide variety of aggregate used in creating our infrastructure, we can be geologists without leaving sight of our homes. Activities Initial Observations Take a closer look at the streets and sidewalks near your home. Get low and close. If you have a magnifying lens, take it with you! Questions to Ask: What do you notice? What patterns do you see? What colors do you see the most of? Is there a color you don’t see at all? What does it feel like? Do all the pieces feel the same? Which is your favorite? Have you seen this somewhere else? Do you think it looked like this when it was first put here? What could have changed it? Texture Discoveries Take a piece of paper and an unwrapped crayon out to the street/sidewalk you’re studying. Lay the paper over the ground and gently rub the unwrapped crayon (on its side) over the paper. This will reveal the texture! Questions to Ask: What does it remind you of? (offer your own answer as well!) What do you think it looks like? Springbrook Nature Center Author: Emily Meyer # For an extra creative challenge, try to turn your textural rubbing into something else! Color it, cut it up, draw over it—whatever feels right! Identification Exploration Use the images below of rocks commonly found in roads and sidewalks to see if any of them are in the sample you’re studying! Questions to Ask: Can you find any of these in our sidewalk/road? What similarities do you see between the pictures and what is here? What differences do you see? Why do you think it’s __________? **It’s not necessary to accurately identify every aggregate rock in the road. The purpose of this activity is to learn how to verbalize reasoning (ex: “I think this is granite because I can see lots of small black bits in it, like the picture”) Granite: Springbrook Nature Center Author: Emily Meyer # Limestone: Basalt: Springbrook Nature Center Author: Emily Meyer # Other Quartzites: Springbrook Nature Center Author: Emily Meyer # Extra Images: If you aren’t able to safely get outside to observe your own streets, there is a supplemental PDF with pictures that could be used to do two of the previous activities. Springbrook Nature Center Author: Emily Meyer # .