D. high and low levels of silica in the different type of lava.
Explanation:
The volcanoes have different types of explosions. Some tend to be highly explosive, some less explosive, some don't have explosions at all, while some have combinations of different eruptions. The reason for this diversity in the eruption types is mostly the composition of the magma, or rather how high is the silica content in it.
Basically, the higher the silica level in the magma the higher the explosiveness, and the lower the silica level the lower the chances of explosiveness. This is the case because the higher amount of silica makes the magma thicker, so the gasses are trapped and they explode, while when the lower silica content makes the magma less thick, so the gasses are not trapped and explosions are lacking.
Answer:
The simplest way to define ecological footprint would be to call it the impact of human activities measured in terms of the area of biologically productive land and water required to produce the goods consumed and to assimilate the wastes generated.
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A family that extends beyond the immediate family, including grandparents, aunts, uncles, and other relatives
Cambrian period do the Appalachian mountains first start to appear. The Paleozoic Era and the Phanerozoic Eon were both preceded by the Cambrian Period.
An crucial turning point in the evolution of life on Earth occurred during the Cambrian Period, when numerous invertebrate species and the first fish-like vertebrates first appeared in the fossil record. The greatest record of Cambrian animal fossils, including soft-bodied creatures, may be found in the Burgess Shale. The Paleozoic era's Cambrian phase saw the most rapid explosion of evolution ever recorded. A staggering diversity of life, including many of the main animal groupings still extant today, emerged during the Cambrian Explosion. The chordates, which include vertebrates (animals with backbones) like humans, were among them. According to some experts, the appearance of predators was made possible by a slight, possibly transient increase in oxygen that abruptly crossed an ecological threshold. Carnivory's emergence would have sparked an evolutionary arms race that produced the explosion of various body kinds and behaviours that now populate the oceans. The team comes to the conclusion that a scarcity of oxygen and toxic hydrogen sulphide killed off a large number of Cambrian species. It is believed that similar circumstances led to the devastating Permian extinction 251 million years ago. According to Gill, there were multiple instances of fast extinction in the second half of the Cambrian.
Learn more about Cambrian period here
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