Sedimentary sandstones and shales, deposited by seas during the Paleozoic and Mesozoic eras (approximately 540 million to 66 million years ago) can be seen in the Gallatin Range and Mount Everts. Sedimentary rocks in Yellowstone tend to erode more easily than the Precambrian rocks. Weathering breaks down earth materials from large sizes to small particles, and happens in place. The freeze/thaw action of ice is one type of weathering common in Yellowstone. Agents of erosion— wind, water, ice, and waves—move weathered materials from one place to another.
[{"rock_types": "Sedimentary sandstones", "era_formed": ["Paleozoic and Mesozoic", "Paleozoic and Mesozoic "]}, {"rock_types": "shales", "era_formed": ["Paleozoic and Mesozoic", "Paleozoic and Mesozoic "]}]
[{"rock_types": "Sedimentary sandstones", "era_formed": "Paleozoic and Mesozoic"}, {"rock_types": "shales", "era_formed": "Paleozoic and Mesozoic"}] [{"rock_types": "Sedimentary", "era_formed": "Paleozoic and Mesozoic"}, {"rock_types": "Precambrian", "era_formed": "n/a"}] [{"rock_types": "Sedimentary sandstones", "era_formed": "Paleozoic and Mesozoic "}] [{"rock_types": "sandstones", "era_formed": "Paleozoic and Mesozoic"}, {"rock_types": "shales", "era_formed": "Paleozoic and Mesozoic "}]