The Associated Press reports on a deadly "rockslide" that has killed dozens of people in Egypt. More exactly, it appears from the photos to be a rockfall, triggered as water from homes at the top of the rocky cliff near Cairo leaked into and weakened the strata there.

See more about the types of landslides.

Granite seems like a simple subject until you study geology. Then granite becomes a deep enigma and a stubborn controversy. But with this new article I hope to bring you the outlines of what granite signifies, not just why it's so popular for countertops. At the very least, you may take a little planetary pride, because granite is planet Earth's signature rock.
_{Salinian granite, King City Calif. — Geology Guide photo}

Classes have already started for a lot of students. Quick, grab yourself some cool wallpaper images for your laptop before someone notices how lame your default Windoze desktop is. (Professors and T.A.s, you too.) I just happen to have a bunch for you to choose from, in handy 800x600, 1024x768 and 1280x1024 sizes. And this just in—the newest batch of wallpapers, the Pebbles and Cobbles portfolio, features some images at 1600x1200 to serve the growing minority of people with that screen size.

These wallpapers are also good background images for presentations. You may make free use of them for desktops and presentations; any other uses fall under my fair use guidelines. I've seen them used in scientific posters at meetings, so I know they're good.
_{Rodeo Beach pebbles — Geology Guide photo}

A California entrepreneur wants to start turning straw into gold by bubbling power-plant fumes through seawater. Industry sources have written about it since 2007, but this month the the story reached Scientific American and, in a less rigorous treatment, the San Francisco Chronicle yesterday.

The process is designed to turn carbon dioxide from the power plant into carbonate in the seawater, which then combines with magnesium and calcium in the seawater to make unspecified carbonate compounds. But those compounds aren't cement, and they can't be turned into cement without driving off at least some of the carbon. So something very important is missing, because the inventor of the process, Stanford prof Brent Constantz, claims that his process pulls half its weight worth of CO₂ from the atmosphere. More precisely, half of the product's mass would be carbon and oxygen in 1-to-2 proportion. Such a material is not cement; it's filler.

Other blogs have written about this, and nobody understands what Constantz is claiming. Add me to them. But Constantz is not a lightweight and deeply understands carbonates as well as how living things deal with them. He may have a secret biocatalyst in the patent-pending process. His firm, Calera, is apparently named after the local Paleocene limestone unit, which crops out in Morgan Hill and Daly City and elsewhere in the Santa Cruz Mountains.

I see a possible waste problem. Bubbling clean flue gas through seawater won't exactly pollute it, but it will charge the water with carbonic acid. This is a major, underappreciated risk associated with CO₂ emissions generally—high CO₂ upsets seawater chemistry so that corals and shellfish and plankton can't build shells. Returning large quantities of carbonated seawater to the ocean will basically bypass the atmosphere and mainline CO₂ directly into the planet's bloodstream. On the other hand, reporters say that heat in the flue gases dries up the water. That's a LOT of water—and what about the salt? Salt is death to concrete.

Basics of Cement and Concrete