Dinosaurs dominated life on Earth for more than 150 million years. In fact, during their reign, other animal species had little chance of playing anything other than secondary roles to the dinosaurs. Then, 65 million years ago they vanished. There are several hypotheses about the disappearance of these “great lizards.” Here is one.

Volcanism

Massive deposits of ancient lava found throughout the world depict an Earth 65- million-years ago where massive volcanic eruptions were commonplace. Lava flows, like those found in the Deccan region of India, reveal a 500,000 year period of active volcanism; a time in which massive amounts of smoke and ash were spewed into Earth’s atmosphere. This global volcanic activity prevented sunlight from reaching Earth’s surface. With the decrease in available sunlight, temperatures around the globe dropped significantly. Plant life declined and photosynthetic activities dropped sharply. Very few species could escape the effects of a perpetually darkened sky and the drastic loss of producers in food webs everywhere on Earth. Dinosaurs as well as many other species could not survive the harsh changes on Earth. In fact, 70% of life on Earth perished at this time.
The end result of extensive volcanism was the extinction of 70% of all species on Earth. What was a pivotal intermediary step in the process of species extinction?
A) death of all animals
B) death of all plant species
C) commonplace volcanic eruptions
D) drastic decline in photosynthesis