Earthquake and Shock Waves
Earthquakes occur when a build-up of pressure or strain between sections of rocks within the earth’s crust is suddenly released, causing minor or severe vibrations on the surface of the land. The point at which layers of rock shift and reposition in relation to one another is called the focus; this is the effective centre of the earthquake. Directly above the focus, a second point called the epicenter marks the corresponding point of highest-intensity shock on the surface.
Dear EarthTalk: What is the environmental impact of so many people now using sites like Facebook and spending so much time online?- Bob Yearling, Paris, TX
The environmental impact of so much online time really boils down to energy usage, which in turn affects the amount of greenhouse gases we pump into our atmosphere. Google, which has been carbon neutral since 2007, has been a real leader in the building of green data centers, even powering them with renewable energy.
Pic Credit: Jurgen Plasser/Flickr
Dear EarthTalk: Is it true that human overpopulation isn’t such a big issue any more as numbers are expected to start declining in a few decades? -- Melinda Mason, Boone, IA
Ever since Thomas Malthus published “An Essay on the Principle of Population” in 1798, positing incorrectly that humans’ proclivity for procreation would exhaust the global food supply within a matter of decades, population growth has been a hot button issue among those contemplating humankind’s future.
Copyright : "Getty Images."
Global average sea levels should rise eight to 34 inches by the year 2100, a much faster pace than the four to 10 inch increase of the past century. Seas rise because of higher global temperatures, melting mountain glaciers and polar ice caps, and other factors. Higher temperatures also cause thermal expansion of ocean water, intensifying the problem.
Dear EarthTalk: Is it true that American kids are going through puberty earlier today than in previous generations, and are there any environmental causes for this? -- Paul Chase, Troy, NY
Research indicates that indeed Americans girls and boys are going through puberty earlier than ever, though the reasons are unclear. Many believe our widespread exposure to synthetic chemicals is at least partly to blame, but it’s hard to pinpoint exactly why our bodies react in certain ways to various environmental stimuli.
Dear EarthTalk: Some green groups are promoting the simple notion of sharing as a way to green communities and combat waste. Can you explain? -- Becky Lipscomb, Centereach, NY
The convergence of environmental awareness and consumer culture has created a whole new movement today whereby sharing is cool. Indeed, some environmentalists view sharing as key to maintaining our quality of life and our sanity in an increasingly cluttered world.
Dear EarthTalk: What is the new documentary film A Fierce Green Fire about and what does the title refer to?- Gloria Howard, Washington, DC
A Fierce Green Fire is a new film documenting the rise of the modern environmental movement from the 1960s through the present day. It premiered at last year’s Sundance Film Festival and will be playing at select theaters across the country beginning in September 2013.