StudySpace: Chemistry 2e.

WHAT A GEOLOGIST SEES: Contact Between Basement and Cover

Near the bottom of the Grand Canyon, we can see the boundary between the sedimentary veneer, or cover (here, a succession of horizontal layers), and the older basement (here, the steep cliff of dark metamorphic rock that goes down to the river). A geologist's sketch emphasizes the contact, or boundary, between cover and basement.For more information, see page 185 and Figure 7.2 in your textbook.

WHAT A GEOLOGIST SEES: Formations in the Grand Canyon

In this photo of the Grand Canyon, we can see five formations. Formations and groups are examples of stratigraphic units. Note that each formation consists of many beds, and that beds range greatly in thickness. The boundaries between units are called "contacts." For more information, see see page 210 and Figure 7.27 in your textbook.

ANIMATION: Formation of Cross Beds

When blowing sand builds into sand dunes in a desert, the sand tumbles up the windward side of the dune, and settles in quieter air on the leeward side. This animation shows how cross beds develop during the deposition of sediment. For more information, see page 212 and Figure 7.29a in your textbook.

WHAT A GEOLOGIST SEES: Formation of Cross Beds in Zion National Park

On this cliff face of sandstone in Zion National Park, we see remnants of ancient sand dunes. Cross beds indicate the wind direction during deposition. For more information, see page 212 and Figure 7.29b in your textbook.

Zoomable Art: The Formation of Sedimentary Rocks

Categories of sedimentary rocks include clastic sedimentary rocks, chemical sedimentary rocks (formed from the precipitation of minerals out of water), and biochemical sedimentary rocks (formed from the shells of organisms). Clastic sedimentary rocks develop when grains (clasts) break off preexisting rock by weathering and erosion and are transported to a new location by wind, water, or ice; the grains are deposited to create sediment layers, which are then cemented together. We distinguish among types of clastic sedimentary rocks on the basis of grain size. For more information, see the Section 7.9 How Do We Recognize Depositional Environments? starting on p. 214 and the Featured Painting on pp. 216-17 in your textbook.

WHAT A GEOLOGIST SEES: Channel Deposits

This exposure shows the lens-like shape of an ancient gravel-filled river channel in cross section. A geologist's sketch emphasizes the channel shape. For more information, see see page 219 and Figure 7.33c-d in your textbook.

ANIMATION: Transgression and Regression

As sea level rises the coast migrates inland (transgression) and retreats seaward (regression), and a record of this movement is preserved in the strata of the sedimentary basin. View 1 shows how this sedimentary sequence is formed; View 2 examines a segment of the landscape millions of years later, after the land has been uplifted and erosion has occurred. For more information, see "Transgression and Regression" starting on p. 224 and Figure 7.37 in your textbook.