Page 394 - Geosystems An Introduction to Physical Geography 4th Canadian Edition

358 part III The Earth–Atmosphere Interface
Laccolith exposed by erosion
Volcanic neck
Aerial view, Shiprock, New Mexico Radiating dike
Landscape view, Shiprock
Sill
Lava
flows (basalt)
Rock strata
Dike
Laccolith (granite)
Dike
Volcano
Magma
Volcanic conduit
Batholith (granite)
Dike
Dike cuts through reddish shale.
Sill in between limestone layers.
▲Figure 12.7 Igneous landforms. Varieties of igneous rocks, both intrusive (below the surface) and extrusive (on the surface), and associated landforms. [Aerial view: Bobbé Christopherson; landscape view: robert Christopherson. Dike: national Park Service. Sill: Arizona geological Survey.]
rocks are divided into several categories—clastic, bio- chemical, organic, and chemical—based on their origin.
Clastic Sedimentary Rocks The formation of clastic sedimentary rock involves several processes. Weathering and erosion, discussed in detail in Chapter 14, disin- tegrate and dissolve existing rock into clasts. Trans- portation by gravity, water, wind, and ice then carries these rock particles across landscapes; at this point the moving material is called sediment. Transport occurs from “higher-energy” sites, where the carrying medium has the energy to pick up and move the material, to “lower-energy” sites, where the sediment is deposited.
Deposition is the process whereby sediment settles out of the transporting medium and results in material dropped along river channels, on beaches, and on ocean bottoms, where it is eventually buried.
Lithification occurs as loose sediment is hard- ened into solid rock. This process involves compaction of buried sediments as the weight of overlying material squeezes out the water and air between clasts and ce- mentation by minerals, which fill any remaining spaces and fuse the clasts—principally quartz, feldspar, and clay minerals—into a coherent mass. The type of cement varies with different environments. Calcium carbonate (CaCO3) is the most common cement, followed by iron
Sill