Name: 9. ( pini Zircon is useful for understanding early earth history because a
ID: 294599 • Letter: N
Question
Name: 9. ( pini Zircon is useful for understanding early earth history because a. It contains relatively rare elements like uranium b. It is relatively resistant to weathering c. It is one of the most common minerals in earth's crust d. A and B e. all of the above poim) During glacial periods, the oceans becomes more enriched in interglacial periods. a. radioactive carbon 14 b. heavy oxygen 18 10. compared to warmer c. light oxygen 16 d. uranium-235 poin The Franciscan Formation of the California Coast contains a significant amount of graywacke sandstone. The source area for the sediment that composes the greywacke was: a. A high desert b. An accretionary wedge c. The uplifted granite of the Sierra Nevada Batholith d. The Sierra Nevada volcanic arc 11. Use the graph below to answer the following questions. 100 90 ao 70 60 O 30 20 4500 9000 13500 18000 22500 Time (millions of years) 12. 11 point) 60% of the original U-238. During what conera did the zrcon form? A zircon crystal contains a. This is not possible, the earth is not that old. b. Mesozoic c. PaleozoicExplanation / Answer
Answer of Question-9
(d) Both A & B
Clarification:
Zircons contain trace amounts of uranium and thorium (from 10 ppm up to 1 wt%) and can be dated using several modern analytical techniques. It can survive Geologic Processes like erosion, transport, even high-grade metamorphism, they contain a rich and varied record of geological processes.
Answer of Question-10
(b) Heavy Oxygen 18
Clarification:
Ocean waters rich in heavy oxygen: During ice ages, cooler temperatures extend toward the equator, so the water vapor containing heavy oxygen rains out of the atmosphere at even lower latitudes than it does under milder conditions. The water vapor containing light oxygen moves toward the poles, eventually condenses, and falls onto the ice sheets where it stays. The water remaining in the ocean develops increasingly higher concentration of heavy oxygen compared to the universal standard, and the ice develops a higher concentration of light oxygen. Thus, high concentrations of heavy oxygen in the ocean tell scientists that light oxygen was trapped in the ice sheets.
Answer of Question-11
(b) Accretionary Wedges
Clarification:
An accretionary wedge or accretionary prism forms from sediments accreted onto the non-subducting tectonic plate at a convergent plate boundary. Most of the material in the accretionary wedge consists of marine sediments scraped off from the downgoing slab of oceanic crust, but in some cases the wedge includes the erosional products of volcanic island arcs formed on the overriding plate.
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Answer of Question-12
(d) Precambrian Era
Clarification:
It occurred 4600 million years ago which is shown in the graph for zircon U-238 form.
The Precambrian (or Pre-Cambrian, sometimes abbreviated p?, or Cryptozoic) is the earliest part of Earth's history, set before the current Phanerozoic Eon. The Precambrian is so named because it preceded the Cambrian, the first period of the Phanerozoic eon, which is named after Cambria, the Latinised name for Wales, where rocks from this age were first studied. The Precambrian accounts for 88% of the Earth's geologic time.
The Precambrian (colored green in the timeline figure) is a supereon that is subdivided into three eons (Hadean, Archean, Proterozoic) of the geologic time scale. It spans from the formation of Earth about 4.6 billion years ago (Ga) to the beginning of the Cambrian Period, about 541 million years ago (Ma), when hard-shelled creatures first appeared in abundance.
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