How It Works - UK (2020-02)

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SPACE

WhathasMarsbeenfeedingOlympus

Monstomakeit rowsobig?

Raising a giant

GIANT

MOUNTAIN

N

amed after the great Mount Olympus in

Greece, Olympus Mons is the tallest peak

in our Solar System. Towering skywards

25 kilometres from its base and spanning

624-kilometres wide, it dwarfs Earth’s highest

mountain, Everest, which is around

8.8-kilometres high. Known as a shield volcano,

Olympus Mons formed over millions of years by

slowly piping core lava over its banks to create a

broad shield appearance. Shield volcanoes are

not exclusive to Mars; many can be found right

here on Earth, like Mauna Loa in Hawaii.

What separates Martian volcanoes from Earth’s

own is the way in which they form. Typically on

Earth, a volcano will grow over a plume of molten

lava below the crust and erupt onto the surface.

However, this process can only occur as long as a

volcano sits above the lava hotspot. Over millions

of years the Earth’s crust naturally shifts and

movesaroundtheplanetata snail’space,around

0.6totencentimetresa year.Thistectonic

movementexposesnewcrusttotheheatof

plumesbelow,anda newvolcanocanform,

almost likea

volcanic

conveyor belt.

However, onMarsthe

planet’s crust remains stationary, which

means that any volcanoes sitting above a

hotspot continually grow.

ICY

SPIRES

Orbitingourlargestplanetar y

neighbour,Jupiter,Callistoisitself

a giantinspace,holdingtherecord

ofthird-largestmooninourSolar

Systemw itha circumferenceatits

equatorof15,144kilometres.What

makesthismoona realspace

oddit yisitscavernousappearance.

Coatedinrockandice,Callisto’s

surfaceishometokilometresofic y

spike-like‘knobs’,reachingupto

around 100 metrestall.Devoidof

volcanoesandw ind,thesespires

havenotbeencreatedinthesame

waytheymighthavebeenif they

wereonEarth.Insteadthesespires

haverisenfromthegroundasa

resultofcontinualbombardment

frommeteorites.Onimpact,dust

andicearethrow nupintotheair,

andovertimehavesettledinto

theseplanetar yicespikes.Dueto

thelackofnaturalerosionfrom

w indandrainthatweseeonEarth,

thesespiresw illbearoundfora

longtime.

Spiresoficy‘knobs’havebeenfoundon

oneofJupiter’smassivemoons

© Getty

NASA’s Galileo spacecraft snapped this

shot of the spire from 138 kilometres

above the surface back in 2001 © NASA/JPL/Arizona State University, Academic Research Lab

Olympus Mons formed over millions

of years as lava continually flowed

over its banks

© NASA/JPL/USGS

OlympusMons,Mars

25 kilometres tall

Mauna Kea, Hawaii

10.2 kilometres tall (4.2

kilometres above sea level and

six kilometres below)

Mount Everest, Asia

8.8 kilometres tall

Putting OlympusMons intoperspective

Plate

motion

Earth

Mars

Noplate

motion

Volcanoes

OnEarth,lavahotspots

eruptthroughthecrust,

forminga seriesof

volcanoesonthesurface.

Crust

Cracksandfracturesin

planetarycrustallow

lavatobreakthrough

tothesurface.

Hotspots

RisingfrombothEarthandMars’

cores,plumesoflavaform

hotspotsbeneaththecrust.

Stationary

OnMarsthecrust

doesnotexperience

anymovement,

resultingin large

shieldvolcanoes,

suchasOlympus

Mons,continually

growingabove

a hotspot.

Movement

Whatseparatesthe

volcanicformationon

Earthcomparedtothat

onMarsis thatthecrust

onEarthis continually

moving,thuscreatinga

seriesofvolcanoesas

thecrustpassesover

thehotspot.