Three trucks began their east-west trek from Swanpool to the NSW border via Myrtleford and Eskdale on Monday as part of the Geological Survey of Victoria.

The vehicles are fitted with steel pads from which seismic waves are being sent 50 kilometres into the earth as they travel eight to 10 kilometres per day.

Geological Survey director Paul McDonald compared the process to an ultrasound with microphones being used to record waves reflected from rock formations.

“There are a lot of unknowns in this space,” Mr McDonald said.

“The Geological Survey has mapped the surface but in the third-dimension, the depth, we have very little knowledge.”

The work follows studies of western and central Victoria over the past decade.

“This is the final piece of the geological puzzle of Victoria, it’s been in the planning for well over five years,” Mr McDonald said.

“We’ve had to plan it around the heat and the ski season.”

It will boost detail of the area’s earth resources, groundwater and seismography.

A crew of 40 to 50 is accompanying the trucks with the route to take in existing roads, logging trails, fire tracks and private properties.

“The geology goes north-south, so for us to get that deep imagery or understanding we collect the information perpendicular to the geology so that’s why we’re going east-west,” Mr McDonald said.

“If we had to collect the information north-south we wouldn’t get a picture of the geology at all.”

Rocks being scrutinised emerged when Australia was part of Gondwanaland, with Mr McDonald saying they predated dinosaurs.

He said the rocks in the east of Victoria were older than those in the west and the 70-day trek would determine a more precise age difference.

The study results will be published online next year following data analysis.