Origin of ancient disaster found
In the 6th century AD, John of Ephesus wrote of a cataclysmic event that devastated coastal Lebanon: "The sea withdrew and retreated from the coastal cities of Phoenicia for a distance of nearly two miles.... A tremendous surge of the sea rushed up to return to its original depths." Tripoli was swamped. Beirut took almost 1,300 years to recover.
Now an international team of geophysicists has traced the origins of the July 9, 551, tsunami to an earthquake along a previously unknown fault roughly four miles off Lebanon's coast. The fault traces the coast for up to 90 miles. The data come from a research cruise in 2003 during which the scientists used high-resolution sonar to map the contours of the sea floor. The evidence shows up as relatively fresh fault scarps along the ocean bottom.
The team also examined stretches of coast whose beaches rise in stair-step fashion out of the Mediterranean – indicators of past quakes that pushed up Lebanon's coast. They estimate that major quakes come in clusters, separated by 1,500 to 1,750 years of relative calm. If that's true, they say, the region is long overdue for a major seismic event. The results appear in the August issue of the journal Geology.
Squid may mean trouble
There's a new squid on the block. And according to marine scientists in California, the change highlights concern over how climate and other environmental changes may be affecting marine conservation and efforts to fish in a sustainable way.
Using deep-sea video surveys, a team from the Monterey Bay Aquarium Research Institute in California reports that the Humboldt squid, a six-foot-long, 110-pound eating machine, appears to have established itself off central California.
These creatures usually inhabit the equatorial Pacific off South America, though they've ventured into subtropical waters and occasionally to latitudes as high as 40 degrees North and South (from off northern California to southern Chile). The video surveys began in 1989 off Monterey. The first squids appeared in 1997, during the onset of El Niño, and hung around until 1998. More were sighted in 1999 and 2000. Then none appeared until 2002, when they arrived and stayed. Now they are being sighted as far north as the Gulf of Alaska.
Among the concerns: The squid appear to be decimating populations of hake, a commercially important fish species that is replacing heavily exploited tuna and billfish at the top of the food chain. In short, the team reports, a fast-reproducing species that can tolerate a range of water temperatures is establishing a population in a part of the ocean already in climatic and ecological stress. The results appear in the current issue of the Proceedings of the National Academy of Sciences.
Researching mastodon family tree
"Cold Case" has nothing on a team of US and European scientists who report they have sequenced the first complete mitochondrial genome for a mastodon – in this case, the long-extinct American mastodon.
Mitochondrian DNA (mDNA) is genetic material housed outside a cell's nucleus. Unlike DNA in the nucleus, mDNA changes little from one generation to the next. It's become a valuable tool for tracing the evolutionary history of organisms. In this case, the DNA comes from a mastodon fossil from Alaska. The fossil is between 50,000 and 130,000 years old.
According to DNA evidence, American mastodons first began to emerge as a separate lineage from modern elephants and woolly mammoths 24 million to 28 million years ago; 19 million years later, African elephants split from the line that would yield woolly mammoths and Asian elephants. These last two shared a common ancestor 6 million to 8 million years ago.
The team notes that some of these divergence dates dovetail with those of humans from African great apes, suggesting that environmental changes leading to more grasslands may have helped touch off the formation of new species in a range of African mammals 7.5 million to 8 million years ago. The results appear in this week's issue of the online journal Public Library of Science Biology.