Larson's father had dispatched him into the darkness from the lighted comfort of a lake-side lodge to check ice-fishing sets placed in holes sprinkled around the big Southcentral lake. Larson followed the beam of a Polaris snowmobile that guided him back along a trail set down earlier in the day.
"I was relatively young and inexperienced," Larson said, but not totally so.
His youth had been shaped by Alaska, and he'd learned a few things from his Boy Scout handbook. He could take care of himself in the woods, but unfortunately, he knew little about the danger he was about to discover.
His introduction came the minute he hit snow infiltrated by water that had come up through cracks in the ice.
"I started sinking, and giving (the snowmachine) more gas, and it just kept bogging down," Larson said. "The first thought was that I was going into the lake."
That didn't happen, but the machine did sink into slush until it was stuck.
"I ended up standing up on top of the seat for four hours until people came out looking for me,'' he said.
Looking back, he thinks he was lucky to have been found in the dark on the wide, blank surface of the lake.
"I don't think I even had a headlamp," Larson said. "I learned never snowmachine without a buddy."
ICE IN THE TUNNELS
Rita Wade knows.
She and husband Brooks were returning from a state public use cabin in the Nancy Lakes State Recreation Area when disaster struck.
"We had real bad overflow," Brooks said, "but we had like four people who were with us who were training for the Susitna 100,'' an annual Susitna Valley endurance race for skiers, mountain bikers, runners and snowshoers.
The group decided to push through the slush encountered beneath the snow on the lakes.
"It was over ankle-deep," Brooks said. "(But) we were basically able to keep going until we reached the cabin."
Everyone figured they'd get there, warm up, regroup, get a good night's sleep and everything would be fine. And it was -- until morning.
"It was below zero, maybe 5 below" the next day, Brooks said, and the snowmachines were frozen solid.
Brooks had propped them up and run them after getting to the cabin in order to get the water from the overflow out. But now it was clear he hadn't run them long enough.
"It was (spinning) free when we went to bed," he said. But the next morning he and Rita had to spend hours pounding ice out of the tunnels of the sleds with an ax handle before they could get the tracks to spin.
WINCHED OUT
Ice in the tunnels of the snowmachines would prove to be only the first problem of the day.
Overnight, the trail the Wade party had broken to reach James Lake had refrozen rutted and rough.
When a ski on Rita's snowmachine hit a rut at the wrong angle, she and the sled were pitched off the trail into the untracked snow beside it.
Her snowmachine quickly burrowed into that snow deep enough to find fresh overflow beneath a layer of white insulation. Now she was seriously stuck.
"It was calf-deep out there," he added. "I had to take a rope and a come-along and walk all the way to shore."
He tied the rope to a tree and used the come-along to winch Rita's sled back onto the hard, frozen trail.
Unless you're in a big group with enough muscle power to manhandle a sled out of almost anything, tools are essential. Double the precautions you take when venturing far from the Alaska road system.
"The first overflow we get into now," Brooks said, "we're turning around and heading back for the car."
If only it were always so easy.
AN AGE-OLD PROBLEM
The problem is, there's no real way to know exactly where or when you are going to encounter overflow, though depressions in the snow atop large lakes or rivers often mean invisible dangers.
And even if you're lucky enough to spot the overflow before you go in, it's often blocking the trail.
When that happens, there are really only two alternatives:
• Hit the gas, and try to buzz across before sinking and getting stuck.
• Shut down and wait for the overflow to freeze, which could take hours or days, depending on weather conditions.
The choices aren't good.
Even those as experienced in wilderness winter travel as the late Archdeacon Hudson Stuck, author of "Ten Thousand Miles With a Dog Sled," can find themselves struggling in water hidden beneath snow.
Wrote Stuck in 1914:
"Subterranean foundations that supply the river do not cease to discharge their waters in the winter, however cold it may be. The pent-up water is strong enough to heave the ice into mounds and, at last, to break forth, spreading far along the frozen surface of the river.
"At times it may be seen gushing out like an artesian well, rising 3 or 4 feet above the surface of the ice, until the pressure is relieved. Sometimes, for many miles at a stretch, the whole river will be covered with a succession of such overflows ... some just bursting forth, some partially frozen, some resolved into solid 'glare' ice."
End up soaked in sub-zero temperatures, and your clothes will quickly turn to a suit of ice, rapidly increasing the risk of hypothermia and frostbite.
Your survival could depend upon the simple skill of building a fire quickly. Unless shelter is nearby, the only way to deal with wet clothes in the cold is to start a fire and dry them out.
ALL KINDS OF DANGERS
Overflow can develop in all sorts of conditions. In addition to lakes and rivers, it can spread from springs, grow on muskegs or mushroom out of creeks that appear to be little more than a trickle.
Few understand overflow much better than ice expert Larry Rundquist of the Alaska Pacific River Forecast Center in Anchorage.
He's quick to point out that the river icing Stuck described isn't really overflow, though it is commonly called that.
Water forced up and over ice to form yet more ice along rivers is what hydrologists usually call "aufeis'' (pronounced off-ice), Rundquist said. Aufeis is a German word that actually means "on ice,'' a succinct description of water flowing over ice.
"Overflow ice,'' Rundquist said, "you get on lakes -- typically when ... you get a big dump of snow.''
Snow weight bends the ice. Cracks develop. Water flows up through the cracks. All sorts of ugly substances develop thereafter, depending on air temperatures and amount of water involved:
• Saturated snow overflow, a sled-trapping slurpee.
• Water under snow, a hidden ambush.
• Glare ice, which can be tricky if your snowmobile lacks good skegs on the skis as well as some studs in the track.
On the Iditarod Trail, the so-called "glacier" near Post River between Rohn and Nikolai is among the more notorious stretches. Ice grows on the surface of several muskeg benches, and it is sometimes so smooth and steep, it can stop snowmobiles without studs.
• Water under ice under snow, a situation that sometimes gives the surface just enough strength to support a snowmachine in motion. Pity the driver who stops in the middle of the lake, only to see his machine break through the crust and settle into water.
DRIVING ON WATER
And then there's water on ice, which, ironically, is sometimes the best place to ride. The danger you can see is usually better than the invisible danger, and a snowmobile can skim along on several inches of water as long as its speed is kept up.
(The same cannot be said of a sled trying to make its way through wet snow. It will tend to bog down, and the more it bogs down, the slower it goes, until it finally stops.)
The only way to avoid getting stuck in such conditions is to drive smooth and fast. Riders who drive fast enough and smooth enough have been known to steer their snowmobiles across an unfrozen lake in the summer and huge ice build-ups on and near rivers.
The latter happens when a river freezes into the gravel beneath, Rundquist noted, and the flowing water has to go somewhere. Usually, it breaks out on top of the ice.
FREEZING BEHAVIOR
Travel is easy when the surface of one of these overflow patches is solidly frozen. But because they're not always flat, problems can arise when there's water on the ice. And it's anybody's guess which one it will be.
"That all depends on the weather pattern," Rundquist said. "It takes a lot of energy to change water into ice. The cold needs to take a lot of energy out. It can take a while, especially if there is enough insulation over it."
Insulation comes in the form of snow, and Rundquist notes that the weather usually has to warm into the 20s for snow. Snow that falls at that temperature can take days to cool back down to the sub-zero temperatures needed to refreeze water trapped beneath.
"A lot of (Bush) pilots out there (are) pretty leery of landing on lakes after a heavy dump of snow because of this," Rundquist said. "Your cold is up in the air. So any saturated snow is going to be freezing from the top down. It may seem pretty firm on top, but if you break through, you're going to be stuck in that slushy snow."
For Rundquist, a student of ice, all of this is intriguing: Overflow, aufeis, muskeg glaciation, freeze-up jam flooding, ice bridging and more. For the average snowmobiler, though, it's just wet, cold and potentially dangerous. The only kind of water a traveler in the Alaska backcountry really wants to see is the kind that falls from the sky in nice, white flakes.