Speaker 1: Welcome to Brainstuff, a production of iHeartRadio, Hey brain Stuff
Speaker 1: Lauren Vogelbam. Here on Earth, plate tectonics build up mountains,
Speaker 1: set off tsunamis, and form volcanoes. To paraphrase the late
Speaker 1: evolutionary biologist Theodosis Dabsansky, nothing about the world's surface makes
Speaker 1: sense except in the light of this process. Earth's outermost
Speaker 1: layer is made up of tectonic plates moving at a
Speaker 1: deliberate pace. Some contain entire continents or subcontinents. Other plates
Speaker 1: lie beneath the ocean. We've talked about how the plates
Speaker 1: can interact in previous episodes, but what's the situation like
Speaker 1: on other planets in our Solar system? Do they experience
Speaker 1: plate tectonics as well? Or is the phenomenon limited to Earth?
Speaker 1: In this respect, our home appears to be kind of unique. Sure,
Speaker 1: other planets are geologically act, but we have yet to
Speaker 1: find an Earth like system of plate tectonics elsewhere. Earth
Speaker 1: has about fifteen moving plates. In contrast, all evidence suggests
Speaker 1: that Mercury is a one plate planet, and this means
Speaker 1: Mercury's surface cannot undergo plate tectonics as we know them.
Speaker 1: On Earth, these separate plates diverge, collide head on, or
Speaker 1: rub past each other. We don't see these things happening
Speaker 1: on Mercury. Nevertheless, its crust isn't exactly in art. Deep
Speaker 1: beneath the surface, Mercury's interior is cooling down. The drop
Speaker 1: in subsurface temperature is forcing the planet's core to contract,
Speaker 1: and its crust is responding in kind. That's right, Mercury
Speaker 1: is shrinking. As the planet gets smaller. Mercury's lone plate
Speaker 1: is crumpling up. If you were to go hiking across
Speaker 1: the surface, pu'ed encounter high cliffs and elongated valleys. These
Speaker 1: are formed when the materials in the crust are pushed
Speaker 1: together and eventually break along what's called a thrust fault.
Speaker 1: Then one part of the crust will be pushed up
Speaker 1: over the other, similar to how separate plates can interact
Speaker 1: on Earth when they're converging. Some of Mercury's scarps, which
Speaker 1: are step like ridges created by faults, are less than
Speaker 1: fifty million years old, making them quite young by geologic standards.
Speaker 1: Their age indicates that Mercury is still experiencing crustal movement.
Speaker 1: For the article, this episode is based on How Stuff Works,
Speaker 1: spoke by email. Clark R. Chapman, a Colorado based astronomer.
Speaker 1: He said Mercury's crust has shrunken a lot and is
Speaker 1: very likely continuing to shrink because the interior is cooling
Speaker 1: and shrinking. A rough analog would be the skin of
Speaker 1: an apple. As the interior of the apple gradually dries
Speaker 1: out and shrinks, it causes the skin of the apple
Speaker 1: to get wrinkled, and this same process is unfolding much
Speaker 1: closer to home. Like Mercury, Earth's Moon is a one
Speaker 1: plate body that's now shrinking as its core cools. The
Speaker 1: makeup of Mars, meanwhile, isn't so certain. The red planet
Speaker 1: contains the Solar System's largest volcano, along with its biggest canyon.
Speaker 1: That canyon, named Vallis Mariners, is some two thousand miles
Speaker 1: long and four hundred miles wide. That's some three thousand
Speaker 1: by six hundred kilometers, and it makes Earth's biggest canyons
Speaker 1: look like cracks in the driveway. Even the Mariana Trench
Speaker 1: doesn't measure up. Mars is also notable for its crustal dichotomy.
Speaker 1: The crust of the southern hemisphere has an average thickness
Speaker 1: of thirty six miles or fifty eight kilometers. The average
Speaker 1: thickness in the northern hemisphere is just twenty miles or
Speaker 1: thirty two kilometers. Could the disparity be the handiwork of
Speaker 1: plate tectonics. There are hypotheses that Mars has two gigantic plates,
Speaker 1: that Vallis Marineris is a boundary between them, and that
Speaker 1: a Martian plateau called the Theiras Rise might have been
Speaker 1: made by a subduction zone, which is a place where
Speaker 1: one plate dives beneath another. Houstuff Works also spoke with
Speaker 1: An Yin, who was a professor of geology at UCLA
Speaker 1: and wrote multiple papers about the surface of Mars. He
Speaker 1: said they are hypotheses supported by what we know, but
Speaker 1: with more data to come in the next couple of decades,
Speaker 1: things may change. When houstuff Work spoke to him, he
Speaker 1: was of the opinion that Mars has a primitive form
Speaker 1: of plate tectonics. However, even if that's true, Mars doesn't
Speaker 1: possess many plates. Also, plate related activity on the red
Speaker 1: planet appears to progress at a much slower rate than
Speaker 1: it does on Earth. But let's move on to Venus.
Speaker 1: This planet's gassy atmosphere makes it a tough one to survey. Still,
Speaker 1: we have learned a few things about its surface, judging
Speaker 1: by some of the craters left behind by meteorites. Its
Speaker 1: present day surface is less than a billion years old.
Speaker 1: Parts of Earth's crust are some four billion years old,
Speaker 1: but age is and everything alike Earth, Venus has its
Speaker 1: own ridges, faults, and possibly active volcanoes. Some researchers think
Speaker 1: that Venus owes much of its topography to prehistoric mantle plumes.
Speaker 1: These are columns of molten rock that sometimes reach a
Speaker 1: planet's crust. When they do, they often generate a hot
Speaker 1: spot of volcanic activity. Here on Earth, the lava released
Speaker 1: by mantle plumes created Iceland and the Hawaiian Islands, with
Speaker 1: the newest, the Big Island, being less than a million
Speaker 1: years old. Some scientists think the existence of plate tectonics
Speaker 1: could be a prerequisite for life. As we've discussed, the
Speaker 1: plates tend to promote volcanic eruptions, which release carbon dioxide
Speaker 1: into the atmosphere. Such emissions help keep Earth's temperature nice
Speaker 1: and stable, and that's just one of the benefits they
Speaker 1: provide to organisms. Who knows Earth is the only planet
Speaker 1: known to harbor life. Maybe its abnormal tectonic makeup is
Speaker 1: one of the reasons why today's episode is based on
Speaker 1: the article is Earth the only planet with tectonic plates?
Speaker 1: On how stuffworks dot com? Written by Mark Mancini. Brain
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