… … Seismic Waves … … Word Search
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S H A K I N G N O I T C E V N O C E E below. Every letter in the grid is used once, and once only.
D O T T O P P O S I T E I N N E R P I
N U R H C D E T E C T E D R O P E I S
U T A I O F L E X I B L E N O R I C M
O E V C R P R I M A R Y O U T E R E O
R R E K E S U R F A C E E E R H T N G
G M L F I E L D S E C O N D A R Y T R
R O S H A D O W A L L Y K N I L S R A
E S L O N G I T U D I N A L A R C E M
D T R E F R A C T I O N N W O D U P S
N T S U R C A M G A M S T A T I O N S
U T R A N S V E R S E S T R A I G H T
longitudinal waves move like the wave along this slinky spring transverse waves move like the wave along this rope
wave direction wave direction
Earthquakes and underground explosions generate waves called _ _ _ _ _ _ _ waves and these can be
recorded using _ _ _ _ _ _ _ _ _ _ _ called seismographs. Seismographs produce graphs of the ground
_ _ _ _ _ _ _ they detect in the form of _ _ _ _ _ _ _ _ _ _ _.
By studying the seismograms produced during many different earthquakes and _ _ _ _ _ _ _ _ _ _ _
explosions, scientists have worked out the structure of the Earth. They have discovered that it consists
of _ _ _ _ _ main parts. The solid _ _ _ _ _ _ _ _ _ part is called the lithosphere or _ _ _ _ _. It's about
seventy-five kilometres _ _ _ _ _ and is made from several large tectonic plates that float on the layer
beneath. The mantle lies just below the lithosphere and extends all the way down to the Earth's core.
Although it's classified as solid, the mantle consists of relatively _ _ _ _ _ _ _ _ rock called magma that
flows a bit like a liquid. _ _ _ _ _ flows very slowly in _ _ _ _ _ _ _ _ _ _ currents because the material
nearest the Earth's incredibly hot centre heats up and rises towards the surface. Beneath the mantle is
the Earth's _ _ _ _ which consists of a liquid _ _ _ _ _ layer and a solid _ _ _ _ _ layer. The core contains
large amounts of _ _ _ _ and nickel and the presence of these magnetic metals accounts for the Earth's
magnetic _ _ _ _ _.
There are three types of seismic waves: p-waves (p for _ _ _ _ _ _ _), s-waves (s for _ _ _ _ _ _ _ _ _)
and _ _ _ _ _ _ _ waves. Surface waves only travel through the Earth's lithosphere and it's these ones
that cause the damage that accompanies earthquakes. P-waves are _ _ _ _ _ _ _ _ _ _ _ _ and move in
similar way to the areas of compression that travel along a pushed _ _ _ _ _ _ spring. S-waves are
_ _ _ _ _ _ _ _ _ _ and move like the wave along a _ _ _ _ that's been flicked _ _ and _ _ _ _. P-waves
are the fastest of the seismic waves, followed by s-waves and then surface waves.
P and s-waves _ _ _ _ _ _ away from the _ _ _ _ _ _ _ _ _ of an earthquake or explosion in _ _ _
directions through the Earth's lithosphere and its interior. As they travel towards distant recording
_ _ _ _ _ _ _ _, both wave types are refracted by the rock they encounter and this _ _ _ _ _ _ _ _ _ _
explains why their paths are always _ _ _ shaped rather than _ _ _ _ _ _ _ _. When they reach the core
of the Earth, p and s-waves behave differently. S-waves cannot travel through the liquid outer core and
are reflected away from it. P-waves, on the other hand, pass through the core emerge from the other
side. This difference in p and s-wave behaviour causes a large s-wave _ _ _ _ _ _ zone on the side of the
Earth _ _ _ _ _ _ _ _ the epicentre of the earthquake or explosion. Only p-waves can pass through the
Earth's core to be _ _ _ _ _ _ _ _ in this shadow zone.
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