Barely five months after the Schifter home on Chappaquiddick was moved back from a rapidly eroding bluff, dramatic changes are taking place again at Wasque where the Norton Point breach continues to have a mind of its own. The breach has retreated 800 feet since late September and as a result, the surf and tides have all but claimed the only other house standing along the same length of the Chappy shoreline, owned by Jerry and Sue Wacks of Lexington.

At the end of last week, movers cleared out the Wacks home. On Monday the Edgartown conservation commission visited the house to see how much time it might have left. Built in 1984 as a weekend and vacation home, the house was once situated on a highland of Chappaquiddick that lay some 1,600 feet from the Atlantic surf.

Eight days ago, the measurement had shortened to 25 feet, and the house lay only a few steps from the edge of a cliff that fell straight down to a tidal channel. On Monday the distance was 21 and a half feet, a loss of land that amounted to nearly a foot a day over just four days.

“It’s an extremely difficult position for them,” said Woody Filley, a Chappy resident who along with Robert Gilkes of Edgartown and Skip Bettencourt of Chappaquiddick has been taking measurements and photographs of the transmogrifications along the ocean-facing Chappaquiddick coastline and the nearby barrier spit of Norton Point for the last six and a half years.

The Wackses declined to comment for the story. Yesterday the conservation commission sent them a letter clearing the way for an emergency demolition permit.

Meanwhile, new erosion is also being documented at the Schifter property two thirds of a mile to the east, and at the nearby fishermen’s parking lot owned by The Trustees of Reservations.

“Yeah, we’re losing a lot of property here,” said Chris Kennedy, Martha’s Vineyard superintendent for the Trustees, during a tour of Wasque this week.

Scientists say the mile-long Atlantic coastline of Chappaquiddick stands out as an extraordinary case study in erosion. “If there’s another place in Massachusetts that’s eroding faster than this one, I can’t think of it,” said Greg Berman, a coastal processes specialist at the Woods Hole Sea Grant and Cape Cod Cooperative Extension.

The forces that will likely cost Dr. and Mrs. Wacks their home at the western end of the Chappy shoreline in coming weeks or days — as well as the colossal effort to move back the much larger Schifter home at the eastern end of the same coastline this spring and summer — all began with a Patriots’ Day storm that battered the Vineyard and the seas around it for two days in April 2007.

A combination of astronomical tides, storm surges and a flattened shoreline caused the part of South Beach known as Norton Point to break open. When intact, the barrier beach connects Chappaquiddick to the Vineyard and divides Katama Bay from the Atlantic ocean. When it opened, floodwaters in the bay burst outward into the sea, creating an inlet that separated Chappaquiddick from Martha’s Vineyard for the first time in 30 years, making Chappy an island on its own.

Openings through Norton Point occur historically. Since the Civil War, according to the Gazette and other records, gales opened Norton Point to the sea in 1886, 1953 and 1976. Manmade openings were also dug in 1921 and 1937 to flush Katama Bay, encourage the growth of shellfish, employ townspeople and allow a speedier trip to the fishing grounds off Chappaquiddick.

Whether natural or manmade, records suggest that most of the openings have behaved in much the same way. Encouraged by the eastward run of the current and sediment along the shore, the inlets and beach migrate toward Chappaquiddick where they encounter contrary tidal forces at Wasque Point and eventually close. This often takes 13 to 17 years.

And as the opening through Norton Point reaches the Chappy land mass, scientists say, the inlet and the tides running through it deprive the Chappaquiddick shoreline of the sand that beaches need to stay in place. They wash away, allowing the currents through the opening and waves from the Atlantic to attack the base of the bluffs along the coastline, shoveling away tons of irretrievable earth, day after day and year after year.

“We’ve lost probably 40 acres since [2007],” Mr. Kennedy said.

Early this week at the Wacks house, the tides through the channel were cutting away the base of the cliff where the modest single-story home has stood for 30 years. Scrub oaks and tongues of earth were falling into the current. In ragged avalanches of ground, sand, roots, trunks and limbs, the land was caving toward the foundation of the house.

It appeared that, barring a longshore Christmas miracle, the house was doomed. “One storm can take a pretty significant amount of upland,” Mr. Filley said. “And there’s not a lot left there.” He continued:

“It’s so sad. And especially for them to have to watch it, almost in slow motion. I’m sure they hold out hope that maybe they’ll get a big hunk of sand coming down and give them that little extra protection that they need. We can just all hope that something like that happens.”

Concern over the fate of the Wacks home began in February 2010 as Norton Point and the opening advanced toward Chappaquiddick. When the house was first built, the walk to the Atlantic surf line went through a heathland of bayberry, scrub and trees, across a Jeep trail, through the dunes and over an expanse of beach to the sea. The trip was a third of a mile. Ten weeks ago, the distance from the house to the edge of the cliffs that dropped down to the channel might have been 50 or 60 feet.

By this summer, though, Norton Point had grown long enough offshore to cross in front of the Wacks cliffs, mostly defending them from assault by the sea. A channel lying between the cliff and Norton Point had lengthened, the saw-like currents through the inlet looked like they were easing, and it appeared that the Wacks house might survive.

“I thought they were going to dodge the bullet three years ago, even when it was starting to erode,” said Mr. Filley. “I said I thought it was going to make it.”

But at the end of September, Norton Point reversed direction, retreating westward by as much as 800 feet over the next eight weeks, according to maps created by Mr. Filley, who frequently walks around the perimeter of the point with a GPS. Suddenly conditions changed again at the Wacks house. The scarp fell away at rates that approached two feet a day, based on measurements taken by Mr. Gilkes.

Now the Wackses have moved out of the house and demolition plans are expected to follow shortly.

The retreat of Norton Point has happened before. In April of last year, according to Mr. Filley, the point backed up 750 feet to the west in about three weeks.

Scientists at the Woods Hole Oceanographic Institution don’t know precisely why. “As far as what’s going on the beach, I don’t think we have a clue,” said Steve Elgar of the Applied Ocean Physics and Engineering department. With Britt Raubenheimer of the same office, he has been studying the Norton Point system for the last two years.

“We can wave our arms and stuff, but part of the issue is . . . we need to do surveys really often,” Mr. Elgar said. “We do them once a year because of money. We miss it all. It’s wiggling around and we take a snapshot. If we hit it at the same wiggle, it doesn’t look any different to us. Or if it’s the opposite wiggle, whoa, it’s a huge difference.”

As the opening moves back and forth, the ramifications play out all along the Atlantic shoreline of Chappaquiddick.

The home of Richard and Jennifer Schifter at the eastern end of the coastline is the most famous example. The epic, emergency effort to save the home this year after the Wasque coastline began to landslide into the ocean at the end of 2011 attracted attention around the country.

Following months of preparations, this summer two mainland companies that specialize in moving large buildings dragged the 8,000-square-foot Schifter house intact, foundation and all, some 280 feet back from the edge of the cliff. The home, guest house, garage and basketball court are now resettling on a crunchy moonscape of sand that stretches across the upland to the edge of the world at Wasque.

Following a prior agreement with the town, workers have removed a bulwark of sand and earth that stuck out into the ocean and briefly protected the house from erosion while the move went on. As with the Wacks home at the opposite end of the Chappy shoreline, a precipice now falls to the Atlantic where the bulkwark lay. Witnesses say the Schifter cliff has lost 20 feet of land since Thanksgiving.

Mr. Kennedy said the new erosion makes sense. “As soon as they removed the sand envelopes, I don’t think we really should be surprised at the amount of erosion, because all of a sudden you had no protection for this sand peninsula that had stuck out, and yet you still had the longshore currents,” he said.

Between the Wacks and Schifter properties lies the fishermen’s parking lot, owned by the Trustees and familiar to generations of anglers. Until the end of 2011, fishermen had walked a 330-foot trail from the parking lot to a picnic area, down a flight of stairs, along a wooden walkway, around the eastern end of a pond and across as much as 300 yards of beach, where they fished for blues and stripers in the rips off Wasque Point.

On Monday the trail from the parking lot to the cliff measured 60 feet and everything else beyond it was long gone. Mr. Kennedy said the Trustees will soon move a snow fence back to the nearest edge of the parking lot to keep visitors and fishermen from walking the remaining 20 steps to the edge. The drop to the ocean measures 30 feet and except at extreme low tides, what lies below is the sea.

Woods Hole scientists say they cannot predict what might happen next at Norton Point or along the Atlantic shoreline of Chappaquiddick.

“My guess is that that process will eventually play itself out,” said Peter Traykovski of the Applied Ocean Physics and Engineering department who is studying the movement of currents and shoals along Muskeget Channel, east of the island. “But you can get these transient interruptions, which is obviously tragic for the people who have properties right in front of them.”

Mr. Kennedy was sanguine.

“To me, am I sad? No. I’m in awe at the sheer scope of the changes that nature has brought here. I feel bad for individuals that are impacted, like the Wackses,” he said. “But I’m delighted that there are properties like this that we allow to have that kind of change. That’s what I tell people who come out here: Accept change. Don’t despair. Don’t lose faith. Change is good.”