
To explain: The reason regarding the Precambrian consisting of fewer divisions than the rest of the time scale (although it accounts for nearly 90 percent of the geologic time), by referring to Figure 22.3 in Chapter 22 in this textbook.

Answer to Problem 1GST
The reason regarding the Precambrian era consisting of fewer divisions than the rest of the time scale is because of having less knowledge about this time period. The primary reason is the absence of fossils in Precambrian rocks; many of these rocks are concealed within continental interiors or have been destroyed by tectonic processes.
Due to the lack in complete geologic record from this time, it is difficult to divide this span into smaller increments without more detailed data.
Explanation of Solution
The 4.5 billion years of the Earth’s history is marked by two major eons, namely the Phanerozoic Eon (in Greek, “visible life”), which started about 541 million years ago and the Precambrian Eon, which started approximately 4 billion years ago. The Precambrian Eon is further divided into Archaen, (‘archaios’ denotes ‘recent’) and Proterozoic Eon (‘proteros’ denotes ‘before’; ‘zoe’ denotes ‘life’).
Although, the Precambrian represents nearly 88 % of the Earth’s history, it is not divided into eras, periods and epochs. The reasons for the lack of detailed time scale are stated below:
- Not knowing enough about the detailed Precambrian history. The past 10 years of the Earth’s history is very well-documented because of its fresh, least distorted, and most observable record. As we go further back in time, the clues and records are more fragmented.
- The Precambrian was dominated by simple organisms like bacteria, algae,
fungi , and worms. These organisms lacked hard parts which did not favor preservation. Owing to this reason, the Precambrian had very little fossil records. Due to the lack of fossils, correlation with the exposed Precambrian rocks is usually difficult. - The Precambrian rocks are extremely old and are subjected to a great deal of change. Most of them are greatly distorted metamorphic rocks, broadly eroded and often hidden beneath the younger geological beds and thus, it makes the interpretation of the past environment difficult because of many clues being destroyed in the original sedimentary rocks.
Want to see more full solutions like this?
Chapter 22 Solutions
Earth: An Introduction to Physical Geology
- Please write the final report in detail with all the components.arrow_forwardProvide two paragraphs on your thoughts of reforestation. Please write in first person.arrow_forward1. Label the zone of saturation, the unsaturated zone, and the water table.2. Describe the shape of the water table in relationship to the shape of the land surface.3. Whenever a substantial amount of water is withdrawn from a well, the water table forms a cone of depression. Label the cone of depression on Figure 8.13. What factors might cause a cone of depression to become larger or smaller?4. Use a pencil to shade the area between the dashed lines labeled A. This zone represents an impermeable lens of clay. Describe what will happen to water that infiltrates to the depth of the clay lens at point A.5. How does the drop in the water table during a drought affect the operation of the well? The blue dashed line in Figure 8.13 represents the level of the water table during a drought.arrow_forward
- PlEaSe HeLp As SoOn As PoSsIbLe Identify and label examples of a point bar, a cutbank, and an oxbow lake on the stereogram in Figure 8.11.arrow_forwardWhich of the following is NOT a natural reservoir for water? trees, lakes, creeks, rivers, atmospherearrow_forward1. Draw an arrow on the map to indicate the direction that the main river, the Genesee, is flowing. (Hint: Use the elevations of the two bench marks [BM] next to the river near the top and bottom of the map to determine your answer.) 2. Use the BM elevations from Question 1 to calculate the approximate gradient of the Genesee River. 3. Use Figure 8.9 to draw a profile along line A-A". Use only index contour lines. 4. Approximately how many feet is the Genesee River above sea level? 5. The path of the Genesee River can best be described as which of the following: a straight course or a meandering course? 6. Which phrase most accurately describes most of the areas beyond the Genesee River Valley: very broad and flat or relatively hilly and dissected? 7. Use the fractional scales on the Angelica topographic map and the Portage, Montana, map (page 136) to answer the following. a. What is the fractional scale for the Angelica map? b. How does this compare to the fractional scale for the…arrow_forward
- 1. Compare the stereogram in Figure 8.7 to the map in Figure 8.6. Then, on the topographic map, outline the area shown in the photo. 2. Is the terrain in Section 14, located on the west side of this map, relatively flat or hilly? Explain. 3. Label the areas that topographically resemble Section 14 on the topographic map as "upland." 4. Describe the topography in the lower half of Section 17, located three sections east of section 14. 5. Section 17 contains a portion of the valley occupied by the Missouri River. Approximately what percentage of the area shown on the map is stream valley (similar to the lower half of Section 17) and what percentage is upland? 6. Which of the following best describes the shape of the Missouri River Valley along the line labeled D.-D': wide valley with a floodplain or steep-sided V-shaped valley with no floodplain?arrow_forwardUse the Portage, Montana, topographic map in Figure 8.6 (on page 136) and the stereogram in Figure 8.7 (on page 137) to complete the following. 1. Compare the stereogram in Figure 8.7 to the map in Figure 8.6. Then, on the topographic map, outline the area shown in the photo. 2. Is the terrain in Section 14, located on the west side of this map, relatively flat or hilly? Explain. 3. Label the areas that topographically resemble Section 14 on the topographic map as "upland." 4. Describe the topography in the lower half of Section 17, located three sections east of section 14. 5. Section 17 contains a portion of the valley occupied by the Missouri River. Approximately what percentage of the area shown on the map is stream valley (similar to the lower half of Section 17) and what percentage is upland? 6. Which of the following best describes the shape of the Missouri River Valley along the line labeled D.-D': wide valley with a floodplain or steep-sided V-shaped valley with no floodplain?…arrow_forwardPlease upload your one to two-page summary about what you learned from the 55-minute Magnetic Storm documentary. H) The Universe Magnetic Storm Threat.... Η The Liver MWgnete storm Threat. Watch later Share HISTORY H Watch on YouTubearrow_forward
- Use the textbook and the internet to complete the following work covering all of the previous material. It will help with a deeper understanding of the material before taking Midterm #1 too. Choose the best bold word/s option for each one given below. Please write out in complete sentences your answers and upload your file. 1. The Earth is a/an open or closed system as far as energy is concerned and a/an open or closed as far as "rocky" material (10 points). 2. Divergent boundaries experience tensional, compressional, or shearing forces creating normal, reverse, or strike-slip faults (10 points). 3. Convergent experience tensional, compressional, or shearing forces creating normal, reverse, or strike-slip faults (10 points). 4. Transform boundaries experience tensional, compressional, or shearing forces creating normal, reverse, or strike-slip faults (10 points). 5. The Himalayas an example of a convergent, divergent, or transform boundary (5 points). 6. The Mid-Atlantic Ridge an…arrow_forwardDiscussion Question: Solar Energy, Seasons, and the Atmospherearrow_forward1. Does urbanization increase or decrease the peak streamflow? 2. What is the effect of urbanization on lag time (the span between when rainfall occurred and when peak stream discharge occurred)? 3. Does total runoff occur over a longer or shorter time span after an area has been urbanized? 4. Based on what you have learned from the hydrographs in Figure 8.4, explain why urban areas often experience more flash-flooding than do rural areas during intense rainfalls.arrow_forward
- Applications and Investigations in Earth Science ...Earth ScienceISBN:9780134746241Author:Edward J. Tarbuck, Frederick K. Lutgens, Dennis G. TasaPublisher:PEARSONExercises for Weather & Climate (9th Edition)Earth ScienceISBN:9780134041360Author:Greg CarbonePublisher:PEARSONEnvironmental ScienceEarth ScienceISBN:9781260153125Author:William P Cunningham Prof., Mary Ann Cunningham ProfessorPublisher:McGraw-Hill Education
- Earth Science (15th Edition)Earth ScienceISBN:9780134543536Author:Edward J. Tarbuck, Frederick K. Lutgens, Dennis G. TasaPublisher:PEARSONEnvironmental Science (MindTap Course List)Earth ScienceISBN:9781337569613Author:G. Tyler Miller, Scott SpoolmanPublisher:Cengage LearningPhysical GeologyEarth ScienceISBN:9781259916823Author:Plummer, Charles C., CARLSON, Diane H., Hammersley, LisaPublisher:Mcgraw-hill Education,





