Pros: 1  Works equally well in open terrain, under cover or in a gym. 2  Accurate on flat or hilly terrain and when making quick, sharp turns (e.g., when trail running or on an indoor track). 3  Lightweight design is sleeker than most GPS-enabled SDMs.
Definitions for mass extinction. Here are all the possible meanings and translations of the word mass extinction. Wiktionary(0.00 / 0 votes)Rate this definition: mass extinction(Noun) A sharp decrease in the total number of species in a relatively short period of time.
A Brief History of Earth. Mass extinctions--when at least half of all species die out in a relatively short time--have happened only a handful of times over the course of our planet's history. The largest mass extinction event occurred around 250 million years ago, when perhaps 95 percent of all species went extinct. Top Five Extinctions