Heavy snow and midday school closures ground Atlanta to a horrible halt Tuesday, spurring historic traffic jams that forced thousands of people to spend the night in cars and makeshift shelters across the metro area. At least one person died in the chaos, countless were stranded without basic necessities, and a baby was born on Interstate 285.

But as local authorities struggled to free the gridlock, even well into Wednesday, an army of white knights mobilized to fill in the gaps with offers of food, shelter and other support. As in many recent disasters, both natural and manmade, social-media networks and old-fashioned good Samaritans proved more nimble than city or county services, many of which were overwhelmed by calls or simply stuck in traffic themselves.

"During states of emergency and other crises, governments and first responders are tied up, and citizens can find themselves on their own in that respect," says Dr. Elizabeth Cohen, a native Atlantan and assistant professor of communication studies at West Virginia University. "But thanks to social media they don't have to fend for themselves."

"Tools like social network sites permit people to share crisis-related information, request help, and mobilize aid relatively quickly," adds Cohen, who researches the psychology of Facebook and other social media. "A person trapped in their car 20 miles from home in freezing temperatures might only have a smartphone at their disposal, but that might be the only thing they need to keep tabs on the status of friends and family, connect with people willing to help in the area, or get tips for staying safe in their vehicle overnight."

The late decision to close schools Tuesday has been blamed for much of the traffic, but teachers and administrators were also among the first to sweep into action, hunkering down in schools with children after buses and parents were stranded on roads:

As news of the crisis spread on social media, it spurred a wave of crowd-sourced relief from a wide range of sources, including offers of free shelter at homes, churches and businesses like CVS, Home Depot and Publix, where people slept in aisles Tuesday night.

Images of the mess on Facebook, Twitter and Instagram also prompted good Samaritans to walk the interstates Tuesday night and Wednesday morning, checking on stranded drivers and offering food, water or other help. "I saw on Facebook people had been out here for 18 hours … so I just thought I'd try to help out any way I could," Matthew Miller told Atlanta's WSB-TV as he handed out food on I-75.

Facebook as 'morale booster'

One of the most robust efforts has been Snowed Out Atlanta, a Facebook group that began early in the crisis and grew to 35,000 members within 12 hours as conditions worsened. While authorities grappled with traffic, the group became a key resource for people to both seek and offer help. "Any Jeepers or 4x4 in Buckhead?" read a typical comment posted Wednesday afternoon, more than 24 hours into the traffic jam. "I need to get my car off Paces Ferry and try to get home before dark. I'm pregnant and have a child at home."

"My dad is still stuck. Going on 21 hours now," another commenter wrote. "Does someone have the national guard number? He has no food or water."

Many posts sought help for elderly or disabled people stuck without food, water and medicine, or sought news about missing friends and family. "My son Matthew is broke down somewhere between Smyrna and Dallas," a parent posted Wednesday, referring to two Atlanta suburbs. "His phone is dead. If anyone is out in that area his name is Matthew Vining and the last we heard he had left the car and was at a motel lobby."

The Facebook group is also a hub of people wanting to help, offering trucks and other equipment to free stuck vehicles or simply food and shelter at homes near interstates. By Wednesday, it was so flooded with offers and requests for help that its creator, Michelle Sollicito of Marietta, Ga., worried its popularity was beginning to negate its usefuless. "This group is getting too big to help people!!" she wrote, explaining her decision to divide the group into a series of regional pages for different parts of metro Atlanta.

Beyond the actual help provided by Snowed Out Atlanta and other social-media threads, professor Cohen says such efforts bolster our sense of community and help ward off despair amid the tedium and misery. As in other recent disasters — from huge events like Superstorm Sandy to local floods and wildfires — the decentralized nature of social-media networks makes them an increasingly important part of rescue and relief.

"The group wasn't simply a networking tool; it was a morale booster," she says. "I think one reason social network sites are so effective at galvanizing a response at the community level is because seeing the crisis unfold in their own personal social network has the effect of bringing the crisis home for people, prompting greater concern and motivating more action."

Russell McLendon ( @russmclendon ) writes about humans and other wildlife.

Social media rallies rescuers in snowy Atlanta
As snow crippled metro Atlanta, social media helped mobilize good Samaritans. Is this the future of disaster relief?