Apr 6th: Mapping the Earth’s Magnetic Crust

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Podcaster: Richard Drumm
Title:
Space Scoop: Mapping the Earth’s Magnetic Crust

Organization:365 Days Of Astronomy

Link : astrosphere.org ; http://unawe.org/kids/unawe1710/

Description: Space scoop, news for children

Our understanding of Saturn’s rings is still evolving. A team of researchers using observations made in 2008 have managed to measure the brightness and temperature of Saturn’s rings in more detail than ever. More detail in mid-infrared images from the ground, that is.

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Bio: Richard Drumm is President of the Charlottesville Astronomical Society and President of 3D – Drumm Digital Design, a video production company with clients such as Kodak, Xerox and GlaxoSmithKline Pharmaceuticals. He was an observer with the UVa Parallax Program at McCormick Observatory in 1981 & 1982. He has found that his greatest passion in life is public outreach astronomy and he pursues it at every opportunity.

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Transcript:
This is the 365 Days of Astronomy Podcast. Today we bring you a new episode in our Space Scoop series. This show is produced in collaboration with Universe Awareness, a program that strives to inspire every child with our wonderful cosmos.

Mapping the Earth’s Magnetic Crust

Earth is surrounded by a huge cocoon that protects us from the dangerous cosmic radiation and particles that bombard our planet.

Without it, life as we know it would not exist, yet it’s totally invisible! This cocoon is Earth’s magnetic field. It’s more of a magnetic shield than field, if you get my drift!

Most of the magnetic field is created by Earth’s molten iron core. However, a small part is created by magnetic rocks closer to the planet’s surface, in the Earth’s crust.

The crust is the solid rock layer of the Earth, which we live on. If the Earth were the size of an apple, the crust would be the skin – it’s very thin compared to the other layers.

Under the oceans it’s about 10 kilometers thick, under the continents – the land – it’s up to 80 kilometers thick. The oceanic and continental crusts have different compositions and properties.

The oceanic crust is basalt-rich and the continental crust has less dense “felsic” rock like granite. Both oceanic & continental crusts are floating on the mantle layer underneath.

The uppermost and most solid mantle is broken into tectonic plates and the crust layers are along for the ride!

Learning about the crust of our home planet is no easy task. We can’t simply drill through it to measure its shape and see what it’s made of.

But ESA’s Swarm satellites are up to the task.

This is the same satellite that just last year discovered a jet stream-like river of liquid iron in Earth’s outer core. It’s flowing westward under Alaska & Siberia, is 420km wide & runs half way around the globe!

Cool!

Swarm is a group of three satellites, Alpha, Bravo & Charlie, orbiting our planet. In this study their job is to examine the weak magnetic field created by Earth’s crust and help us understand it better.

The satellites were launched by ESA in 2013 from the Plesetsk Cosmodrome, north of Moscow, Russia.

After three years of collecting data with Swarm, a computer generated image is the outcome. It’s the most detailed map of the Earth’s magnetic field ever made!

A link to the image is in today’s show notes.

The areas where the magnetic field is weaker are shown in blue, and the strongest regions are red. These differences are caused by the shape of Earth’s crust.

Lots of interesting and peculiar spots have been discovered. One is located near the city of Bangui in the Central African Republic, where the magnetic field is particularly strong.

The cause is still unknown, but some scientists think it’s the result of a meteorite impact more than 540 million years ago!

Hey, Here’s A Cool Fact:
One of the coolest features of this new map are the stripes across the ocean floor. These are evidence of times when our planet’s magnetic field flipped, and the north and south poles switched position.

When new crust is generated through volcanic activity, mainly along the ocean floor ridges, iron-rich minerals in the magma are oriented towards magnetic north.

As the lava solidifies the magnetic orientation of these minerals is locked in place, thus capturing a ‘snapshot’ of the magnetic field in the state it was in when the rocks cooled.

Since magnetic poles flip back and forth over time, the solidified minerals form ‘stripes’ of a sort on the seafloor and provide a record of Earth’s magnetic history.

Our magnetic field has been weakening in recent centuries. This could be an indication of an impending pole reversal. Or maybe not, time will tell.

Pole reversals happen once every few hundred thousand years. When it next happens, your compass’s north end of its needle will point south instead of north!

That’s it. That’s all that will happen.

There won’t be any mass extinction event to go with the reversal. The reversals in the past have not been accompanied by extinctions, so there’s no cause for alarm.

Thank you for listening to the 365 Days of Astronomy Podcast!

End of podcast:

365 Days of Astronomy
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The 365 Days of Astronomy Podcast is produced by Astrosphere New Media. Audio post-production by Richard Drumm. Bandwidth donated by libsyn.com and wizzard media. You may reproduce and distribute this audio for non-commercial purposes. Please consider supporting the podcast with a few dollars (or Euros!). Visit us on the web at 365DaysOfAstronomy.org or email us at info@365DaysOfAstronomy.org.  This year we will celebrate more discoveries and stories from the universe. Join us and share your story. Until tomorrow! Goodbye!

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