A geophysical survey of Ireland has revealed possible ancient volcanoes in Co. Westmeath.
The Tellus Understanding Underground survey has been sending planes loaded with equipment into Irish airspace since 2011.
It is being paid for by the government, and it is beginning to yield some interesting results.
During 2014, scientists flew some 123 flights over the north Midlands region.
They found evidence of volcanoes south of Mullingar buried for the last 300 million years ago, and the survey has also revealed areas of possible mineral excavation.
Results from the Tellus airborne survey of the North Midlands region. Map: Tellus Understanding Underground survey
Flying at 90 metres, technology used on the survey aircraft sensed geological features not apparent from conventional mapping techniques, effectively ‘seeing through’ Ireland’s often deep glacial deposits and extensive peat cover.
The maps produced clearly show a high area of magnetic anomaly (orange circle) in the region of Mullingar, surrounded by an even higher ring of magnetic activity (pink area).
Fig: Tellus Understanding Underground survey
The cluster of small magnetic bodies indicates 330 million-year-old volcanoes on the Westmeath/Offaly border.
Mineral deposits
The survey maps also show prominent bands of highly magnetic volcanic rocks several kilometres deep near Strokestown Co. Roscommon, which are associated with a major geological fault that can be traced through Ireland to Scotland.
These structures are known to be important in the development of mineral deposits and their location will be of considerable interest to exploration companies.
Ray Scanlon, Principal Geologist at the Geological Survey of Ireland, says there is a practical use for the data: "An understanding of Ireland’s geology is vital for environmental, health and economic reasons, and the data will be welcomed by a broad range of stakeholders for agricultural, radon prevention, groundwater protection and mineral exploration purposes."
Tellus's low-flying plane will continue to collect chemical and geophysical data from southern Ireland throughout the Autumn and winter.
The survey team is currently concentrating on counties Meath, Kildare, Offaly, rural Dublin and northern parts of Laois and Wicklow.
The information gathered will be used to inform policies on the environment and natural resources.
The project, run by the Geological Survey of Ireland, involves a low-flying survey aircraft and a ground-based sampling programme.
Fig shows flying heights of survey plane. Image: Tellus Understanding Underground survey
The Tellus survey plane flies at a low altitude because the instruments on board the plane can sense the properties of soil and rocks more accurately at a low altitude.
The crew uses a magnetometer mounted in a rod on the back of the plane to measure variations in the Earth’s magnetic field.
There is also a gamma ray detector on board to measure the natural radioactivity of shallow soil and rocks.
A frequency-domain (EM) system that sends out signals to the earth is set up on one wing. A receiver on the other wing pod will measure small changes in this signal as it passes through different types of rocks and soil.
