The phrase "ago when a vast" is not correct and does not form a coherent expression in written English.
It appears to be an incomplete thought and lacks clarity, making it unusable in its current form.
Example: "It was a long time ago when a vast change occurred in society."
Alternatives: "long ago when a great" or "in the past when a significant".
The landforms of Pennsylvania had their origin about 500 million years ago, when a vast interior sea, up to several hundred miles wide, occupied the area from New England to Alabama.
A half-century ago, when a vast new shopping center debuted a mile east of the Las Vegas Strip, anyone who mattered came by.
That made sense 75 years ago, when a relatively small number of corporations — oil and coal companies, steel producers, car makers — controlled a vast segment of the work force and when government was a comparatively anemic enterprise.
A few decades ago, when the vast majority of Indians lived in the countryside and when agriculture represented around a third of national income, all of this would perhaps have been cause for less concern.
Still, Lt. Col. Avital Leibovich said "the military really did a revolution" since she joined up more than 20 years ago, when the vast majority of female soldiers served in human resources or educational posts.
The logic was a good one: the student population is a much more diverse population than thirty or forty years ago when the vast majority of students came from affluent families and did not need to work while attending college.
The Aussies and Kiwis got in on the halal action years ago when the vast majority of their abattoirs - 95% in New Zealand - went halal in order to cater to the insatiable demand for beef and lamb in south-east Asia and the Middle East, where over 90% of non-poultry meat is imported.
None except an unusual commemoration granted at a modest opening ceremony two months ago when a vast former landfill site on the edge of Tel Aviv was renamed Ariel Sharon Park.
Dawn on 21 June will see the ancient megaliths of Stonehenge bustling with white-robed Druids intent on viewing the Sun rising behind the outlying Heel Stone – just as our ancestors did millennia ago when they raised this vast structure to celebrate midsummer's morning.
If correct, this means the mammoth was alive during the heyday of woolly mammoths 42,000 to 44,000 years ago when they roamed the vast open grasslands of the northern steppe of the Siberian Arctic, Pitulko says.
A century and a half ago, when the Religious Society of Friends built a meetinghouse in what was then the City of Brooklyn, the surrounding landscape seemed vast.
