Analyze the piece of laver cake in Fig. A8.1.1. Each side of the block of cake i
ID: 287049 • Letter: A
Question
Analyze the piece of laver cake in Fig. A8.1.1. Each side of the block of cake is a vertical cross-section of the layers. Also notice the surfaces between the layers, where two different layers touch each other. Geologists refer to surfaces between layers or other bodies of rock as contacts. 1. Think about the process used to construct the layer cake from depositing the first layer to depositing the last laver On the left edge of the cake, number the layers to show the sequence of steps in which they were deposited to make the layer cake from I (first step) to "n" (the number of the last step) 2. Using a pen, draw lines on the layer cake to mark all of the contacts between layers. Then place arrows along the right edge of the cake that point to each contact. Label each arrow to show its relative age from 1 for the first or oldest contact to "n"- the number corresponding to the Figure AB.1.1 youngest contact. Figure A8.1.2 shows an outcrop about 5 meters thick near Sedona, Arizona. The red rock in Fig. A8.1.2 is an ancient soil called a paleosol. The brown layer in which grass is rooted near the top of the photo is modern soil. The blocky brown-gray rock with wide fractures is an ancient lava flow. This outcrop is a natural geologic cross-section of rock layers, analogous to the cake 1. Which layer is the oldest? How do you know? 2. Using a pen, carefully draw lines on Fig. A8.1.2 that mark the position of (a) the contact between the red ancient soil and the lava flow (b) the contact between the top of the lava flow and the base of the darker brown modern soil in which grass is growing 3. Notice the fractures that cut across the lava flow layer Are they older or younger than the lava flow? How do you know? 4. Notice that clasts of the lava flow are included in the brown soil. Are they older or younger than the brown soil? How do you know? Figure A8.1.2Explanation / Answer
In case of question 1 of figure AB 1.2, the older rock is paleosol beause according to law of superpostion layers are deposited from older to younger upward.