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Several basic geologic principles can be applied to resolving the order of events leading to the formation of rocks and landscape features.

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(See section 1.10 in Chapter 1 for a discussion on geologic time.) Bedrock is the solid rock that occurs beneath soil or alluvium (unconsolidated sediments) that coved the surface of the land in most locations.

In some places the bedrock is exposed as rocky outcrops scattered across the landscape, particularly in mountainous areas or along stream canyons.

Examples of sediment include gravel, sand, silt, clay, mud (mix of sand, silt, and clay), soil, lime mud, and ooze.

Sediments are , but they may become rocks through heating, compaction, and cementation. Sedimentary rocks are rocks that have formed over time through the deposition and solidification of sediment, especially sediment transported by water (rivers, lakes, and oceans), ice ( glaciers), and wind (Figure 3-8).

The term outcrop is used to describe a location where bedrock is exposed (or crops out).

Why do landscapes in different areas have unique characteristics? Landscapes change from one region to the next because of the composition and character of bedrock changes from place to place.Examples of igneous rocks include granite, gabbro, and basalt.Rocks of igneous origin are discussed in Chapter 7.Sediments are solid fragments of inorganic or organic material that come from the weathering of rock and soil erosion, and are carried and deposited by wind, water, or ice (Figure 3-7).Sediments may be made up of rock fragments ranging is size from boulders down to microscopic particles, and may contain organic matter.The word igneous applies to any rock or mineral that solidified from molten or partly molten material (referring to magma underground or lava on the surface).

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