Taxonomy term

Space is deadly, and the explorers who risk their lives to venture farther into these depths rank among the bravest heroes of all time. In “Mankind Beyond Earth: The History, Science, and Future of Human Space Exploration,” Claude A. Piantadosi portrays the history and future of space exploration through the lens of space medicine, which reminds us of the many threats to the human body that await as we venture away from our planet.

The 2016 book, “Tipping Point for Planet Earth,” by paleoecologists Anthony D. Barnosky and Elizabeth A. Hadly, is a serious book on a serious topic, and a well-written, one-stop resource for anyone who wants to understand a host of looming problems. The book focuses on the alarming number of worrisome planetary trends now underway, mainly as a result of the convergence of population growth and human-induced global warming. Chapters cover people (population growth), “stuff” (increased purchases of material goods), storms, hunger, thirst (failing water supplies, clean or not), toxins, disease and war. These trends have merited serious attention from environmental scientists and deserve the same from politicians. Whether they are tipping points, however, is a point of contention.

“Hope for the unexpected.” This motto has pulled paleoclimatologist Gifford H. Miller to remote corners of the world to conduct fieldwork for more than half a century. Miller, a professor of geological sciences at the University of Colorado Boulder (CU) and associate director of the Institute for Arctic and Alpine Research, thrives on the pursuit of knowledge, asking tough questions about the global climate system whose answers have far-reaching implications. But it’s the thrill of unexpected discoveries — of which he’s made many — that keep him returning for more. His discoveries, including the extinction timing of giant birds in Australia, the existence of “zombie mosses” that document the life-cycle of Arctic ice caps, and the finding of lake sediments that tell the story of Iceland’s deglaciation, have led to advances in our understanding of Earth’s climate history and the role humans have played in it.

Fluorspar, or fluorite, occurs in a variety of geological environments and is deposited under a wide range of chemical and physical conditions, but commercial sources are primarily hydrothermal. The most common deposits occur as veins, mantos (replacement strata-bound orebodies) or replacement deposits. Other important deposits include stockworks and fillings in shattered zones, carbonatite and alkalic rock complexes, residual concentrations resulting from the weathering of primary deposits, and recoverable gangue in base metal deposits.