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Dry, Hot Weather Uncovers Secrets

Newgrange, County Meath, Ireland —(Map)

Last week, ran a story about a worldwide heat wave. That heat wave is still going on and it’s very serious. In many parts of the world, it’s causing huge problems. For example, California and Greece have both had bad wildfires that have damaged buildings, made people leave their homes, and even killed people.

But this story is about a less harmful side of heat waves, and the interesting surprises they can bring. Long periods of hot, dry weather can change the way that plants in farm fields grow. And this can show secrets about things that are hidden under the ground. These are called “cropmarks”.

Cropmarks show up when it is hot and dry.Plants grow differently depending on what's underneath.
Cropmarks show up when it is hot and dry.
Plants grow differently depending on what’s underneath.
(Source: cliché J. Dassié, via Wikimedia Commons.)

Long ago, some groups of people arranged stones in special ways, like Stonehenge. Because of Stonehenge, these are called “henges”. At other times in the past, people made buildings from wood and dirt. And at still other times, of course, stronger buildings were made with stone or brick.

All of these people – the henge makers, the wood and earth house people, and the more modern builders might have also dug holes or ditches.

Stonehenge in Wiltshire, England is probably the most famous henge.
Stonehenge in Wiltshire, England is probably the most famous henge.
Others may have been covered over.
(Source: garethwiscombe via Wikimedia Commons.)

But many of these things have disappeared. Over time, the buildings might fall down or be torn down. The wood could rot, the dirt could wash away. The ditches and holes might be filled in and the stones might be covered over.

In many places the land can become level again and show no signs of what was there before. That’s what happened in many areas now used for farmland in Europe.

But the hot, dry weather is now giving away some of those secrets. The heat has been affecting crops (plants that farmers grow) in different ways, depending on what’s beneath them.

Things below ground can affect the way plants grow above ground.
Things below ground can affect the way plants grow above ground.
(Source: Befana,

In places where ditches or holes got covered over, there is extra dirt. This dirt holds water for longer, so crops grow better there. In places where there are stones underground, the dirt dries out more quickly than the land around it.

Usually these differences are small and won’t be noticed by someone who is looking at the field from the ground.

But now, people are taking pictures with flying drones. Drones are small aircraft that can be flown and controlled by someone on the ground.

A drone hovering in mid-air.
Drones let people take pictures from high up.
From up above, the cropmarks can be seen.
(Source: Jason Blackeye jeisblack, via Wikimedia Commons.)

When you look at the crops from the sky, things look very different. Instead of a solid color, the plants show the secrets of things hidden under the ground.

When Anthony Murphy and Ken Williams flew a drone near Newgrange on July 10, they weren’t expecting to find a henge that no one had discovered yet. But that’s exactly what they found.

Anthony Murphy and Ken Williams found this henge with their drone.

It’s not just very old history that’s coming back. Clumber Park in England used to have a huge house on it. The house was torn down in 1938. Now the outlines of its buildings are showing up again. The heat is killing plants where the stones that used to support the house were left in the ground.

The people who run Clumber Park posted pictures showing the outlines of the old house.

These are just two examples of cropmarks uncovered by the heat wave, but there are many more across Europe. People are using drones and looking hard for cropmarks now. They have to do it now, because once it starts to rain or the weather cools down, the cropmarks will disappear.


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