The type of rocks you live near could greatly affect how much your area could be damaged by massive solar flares in future, a study has found.

Usually all eyes are on the Sun in anticipation of a serious solar storm that threatens to incinerate delicate technology across the globe.

Some are looking the other way back at our own planet though, and really, we ought to be grateful. It turns out geology could decide what survives and what fries, so researchers are busy mapping the rocks underfoot to see who is at risk of a techno-inferno when the big one strikes.

Jeffrey Love is a geophysicist with the US Geological Survey (USGS) in Denver, Colorado who has a passion for connecting the high above with the far below.

He has been slowly constructing a picture of the arrangement of the rocks making up the North American continent that would buzz with electromagnetic activity in the event of extreme geomagnetic activity spilling from the Sun.

Having locations of potentially electromagnetically active geology is all well and good. But to work out exactly what this means in real-world terms, it's important to calibrate that activity with actual solar storms.

So late last year, Love and his team added another piece of the puzzle to describe which parts of the continent we should expect to be hotspots of destruction.

To do this, the researchers compared records of solar storms with variations in geomagnetic fields as measured by several observatories, quantifying regions of geoelectrical activity over time.

The differences between regions were far from trivial, with rocks in some environments making that electrical activity up to 100 times worse than in others.

"In the grand scheme of things, doing these surveys and collecting the geomagnetic data is not very expensive," Love told Robin George Andrews at National Geographic. "But it takes initiative to do it."

We're super grateful to any researcher who does take that initiative. As time passes the risk of a devastating geomagnetic storm rises along with our dependency on technology, making for the ultimate ticking time bomb.

Such an event would start as a magnetic 'hole' opening in our Sun's corona, channelling a wind of charged particles towards our general direction.

Earth's magnetic cage usually does a commendable job shielding us from the sun-showers of plasma that sprinkle our planet, even managing to handle the occasional vigorous downpours that strike from time to time.

Every roof has its limits, though, and our magnetosphere is no exception.

As its gutters overflow with rivers of protons and electrons ejected from the Sun at near light speed, intense fields are generated, driving electrical currents far below.

Sometimes the effects are relatively minor, but not always. Recently declassified US naval documents describe the peculiar detonation of dozens of sea mines off the Vietnam coast in 1972, since attributed to solar activity sparking off their magnetic sensors.

And there have been hints of far more damaging consequences too. While technology was barely in its infancy in 1859, a powerful coronal mass ejection overwhelmed telegraph wires, shocking operators and sparking fires in what's famously known as the Carrington Event.

More than a century on, our world is cocooned in a fine web of wire that transports power and telecommunications signals into every corner of the globe. That network is especially vulnerable to solar storms, if one strikes that's powerful enough.

Those thin stretches of metal aren't the only materials that can transmit currents of electricity, either. So long as it's made of the right kinds of minerals, voltages can also be induced in the planet's crust.

Water-logged slabs of porous sedimentary rock are capable of conduction, for example.

If you think that means you'd be safer moving to a city perched on top of a giant insulator like a field of granite, think again. Under the right conditions, they could help short circuit power-grids running across their surface.

The interface between an ocean's waters and the insulation of a sandy shoreline also poses risks of currents diverting and building, putting nearby power grids at greater risk.

Depending on how a region's geological jigsaw puzzle locks together, sections of technological infrastructure can either be supercharged with current during periods of intense solar activity, or relatively protected from harm.

South England has enough sedimentary rock to weather a solar storm with relative ease, compared with the electrically-resistant Appalachians in North America, which could easily blow out any grid crossing the mountain range.

Armed with the details of a good geoelectrical survey, authorities will be better prepared to plan for powerful solar storms that are bound to hit.

Because they are coming. And when a big one strikes, it won't be pretty.

This research was published in Space Weather.