Answer:
The answer is Option C: Index fossils.
Explanation:
Index fossils are used to identify geologic periods or faunal stages in rock layers. These fossils must have a wide geographic distribution and manifest obvious evolutionary trends to help geologists and others who need this geological data to better understand the time scale and to pinpoint a time period. For example, ammonites were common during the Mesozoic Era, but they were extinct by the Cretaceous period. Geologists would use ammonites to help determine this time frame if present.
Because with maps they knew where to go , without them they will be lost
Answer:
c) No UV light until spring
Explanation:
According to research, chlorofluorocarbons also known as CFCs, are chemicals that are mainly responsible for the destruction of the ozone gas.
<em><u>This is all due to the interaction of different factors, and not only because of the presence of UV. </u></em>
In Antarctica, the ozone levels become significantly reduced during spring because of these chemicals that contain chlorine, producing a hole where cool air becomes trapped. This air produces clouds that are responsible of the release of chlorine from the CFCs, an extremely important process of the formation of an ozone hole. The more clouds there are, the more gases are released, and the worse the ozone hole will be in spring.
Because the sun rises and becomes more intense during spring, it degrades these gases and releases the free radicals of chlorine, which are highly detrimental for the ozone layer as they destroy numerous molecules of ozone. By the beginning of summer, there is a higher amount of ozone that comes from other areas which help fill the ozone hole.
Answer:
Every river is part of a larger system—a watershed, which is the land drained by a river and its tributaries. Rivers are large natural streams of water flowing in channels and emptying into larger bodies of water.A tributary is a smaller stream or river that joins a larger or main river.
