pThis scheme was developed in 1937 but became more useful when mass spectrometers were improved in the late 1950s and early 1960s. This technique is used on ferromagnesian (iron/magnesium-containing) minerals such as micas and amphiboles or on limestones which also contain abundant strontium. However, both Rb and Sr easily follow fluids that move through rocks or escape during some types of metamorphism./p
pRadiocarbon dating measures the ratio of Carbon-14 to Carbon-12 , this method is known as measuring the presence of a short-life radioactive element. This method of dating can be used to determine the age of organic material up to 50,000 years old and is especially useful in determining the age of ice age fossils. Assigning numeric ages for units of the Layered Paleozoic Rocks was the most difficult. Because no single stratigraphic name exists for this set, Layered Paleozoic Rocks is also an informal term; nevertheless, their rock type, age, and overall geologic setting naturally package them together. No reliable radiometric dates exist for these sedimentary rocks, so their ages are constrained by index fossils. Units with richer fossil records have more precise age constraints./p
pExplain each of your choices.A 4 billion year old piece of granite. In 1892, William Thomson calculated the age of Earth in a systematic fashion (Figure 11.24). He assumed that the Earth began as a ball of molten rock, which has steadily cooled over time. From these assumptions, he calculated that the Earth was 100 million years old./p
h2Radiometric dating/h2
pThe technique has been useful for dating fairly young geological materials and deposits containing the bones of human ancestors. One example is that by measuring how much sediment a stream deposited in a year, a geologist might try to determine how long it took for a stream to deposit an ancient sediment layer. Not surprisingly, these methods resulted in wildly different estimates. A relatively good estimate was produced by the British geologist Charles Lyell, who thought that 240 million years had passed since the appearance of the first animals with shells. Today scientists know that this event occurred about 530 million years ago./p
h3This butterfly is the first U.S. insect known to go extinct because of people/h3
pWhile the most common form of carbon has six neutrons, carbon-14 has two extra. That makes the isotope heavier and much a href= less stable than the most common carbon form. While the electron escapes, the proton remains part of the atom./p

pThe stone pillars in the enclosures at Göbekli Tepe are T-shaped, similar to other Pre-Pottery Neolithic sites in the region. Unlike at these other sites, however, many of the pillars are carved – typically in low relief, though sometimes in high relief. Most carvings depict animals, mostly serpents, foxes, and boars, but also gazelle, mouflon , onager, ducks, and vultures./p
pThe album was commercially successful, and while it did not sell as well as Room for Squares, it peaked at number one on the US Billboard 200 chart. The song Daughters won the 2005 Grammy for Song of the Year, and reached #1 on the Billboard Adult Pop Songs chart and #19 on the Billboard Hot 100. He dedicated the award to his grandmother, Annie Hoffman, who had died in May 2004. On February 9, 2009, Mayer told Ellen DeGeneres that he thought he should not have won the Grammy for Song of the year because he thought that Alicia Keys’ If I Ain’t Got You was the better song. Because of this, he removed the top half of the Grammy and gave it to Keys, and kept the bottom part for himself. At the 37th Annual Songwriters Hall of Fame Induction Ceremony in 2006, Mayer received the Hal David Starlight Award./p
pSo, for example, every carbon atom contains six protons and six electrons, but the number of neutrons in each nucleus can be six, seven, or even eight. Therefore, carbon has three isotopes, which are specified as carbon-12, carbon-13 and carbon-14 . The same techniques of radiometric dating have been used on those rocks. All the data from Earth and beyond has led to the estimated age of 4.5 billion years for our planet. The oldest material of terrestrial origin that has been dated is a zircon mineral of 4.404 ±0.008 Ga enclosed in a metamorphosed sandstone conglomerate in the Jack Hills of the Narryer Gneiss Terrane of Western Australia. The 4.404 ±0.008 Ga zircon is a slight outlier, with the oldest consistently dated zircon falling closer to 4.35 Ga./p
pThis pattern of growth results in alternating bands of light-colored, low density “early wood” and dark, high density “late wood”. Each dark band represents a winter; by counting rings it is possible to find the age of the tree (Figure 11.22). The width of a series of growth rings can give clues to past climates and various disruptions such as forest fires. Droughts and other variations in the climate make the tree grow slower or faster than normal, which shows up in the widths of the tree rings. These tree ring variations will appear in all trees growing in a certain region, so scientists can match up the growth rings of living and dead trees. Using logs recovered from old buildings and ancient ruins, scientists have been able to compare tree rings to create a continuous record of tree rings over the past 2,000 years./p
pAs such, rocks from early lunar history still sit on the surface of the moon. Samples returned from the Apollo and Luna missions revealed ages between 4.4 billion and 4.5 billion years, helping to constrain the age of Earth. How the moon formed is a matter of debate; while the dominant theory suggests a Mars-size object crashed into Earth and the fragments eventually coalesced into the moon, other theories suggest that the moon formed before Earth. In an effort to further refine the age of Earth, scientists began to look outward. The material that formed thesolar systemwas a cloud of dust and gas that surrounded the young sun. Gravitational interactions coalesced this material into the planets and moons at about the same time./p