A natural landmark in the Yorkshire Dales which inspired Wordsworth to write a gloomy sonnet is more than three times older than originally thought, according to new research.

Malham Cove, a curving limestone cliff 1,000ft wide and 250ft high, has inspired awe in tourists and walkers for centuries in a landscape, which, on a good day, gleams silver with its distinctive rock.

Until now, it has always been believed that the cove was formed in the last ice age and is about 14,000 years old. But evidence gleaned from stalagmites suggests that the cove is the work of an earlier ice age and is at least 50,000 years old.

Whether the news would have cheered up Wordsworth is doubtful. His sonnet is a lament that the cove, "this theatric structure", had not formed itself into a full circle:

Was the aim frustrated by
force or guile,
When giants scooped from out
the rocky ground,
Tier under tier, this semicirque
profound?

Wordsworth was wrong: Malham Cove was made by ice not giants. Phillip Murphy, a cave diver and earth sciences technician at the University of Leeds, is more interested in the cove's age than its shape and mythic origins.

"I have been caving for years and I have done a lot of research on caves in Yorkshire," he said yesterday. "One of the things that we are finding is that the caves are a lot older than was previously thought."

The key to dating Malham Cove was a stalagmite found in a flooded cave at its base.

"Stalagmites are not formed in glacial periods as freezing temperatures above and below ground mean there is no moving water," Mr Murphy said.

"So the Malham stalagmite must have been formed during a warm period between a glaciation which formed the cove and a later one which deposited silt at the base of the cove and blocked the entrance to the cave, which then flooded."

Alf Latham, an archaeologist at the University of Liverpool, used radiometric dating to discover that the stalagmite was about 26,000 years old.

That proved that the cave system was reflooded after the last ice age when, 20,000 years ago, glaciers slithered south, stopped at Leeds and created the dales landscape.

It also proved that Malham Cove must have been formed more than 50,000 years ago, predating the last ice age and the warm period before it.

If the cove made Wordsworth feel miserable, it gave Charles Kingsley an idea for a story.

He looked at the vertical stripes formed by lichens and mosses and thought they could have been made by a soot-caked chimney sweep slithering down the rock face. He went on to write The Water Babies.