Page 242 - Big Ideas Year 10 sciPAD 2025
P. 242

PHOTOCOPYING PROHIBITED
© Silverback Academic Media
242 SCIPAD - BIG IDEAS - BOOK 2
EARTH SYSTEMS
Tsunami
The term ‘tsunami’ comes from the Japanese words ‘tsu’ meaning “harbour”
and ‘nami’, meaning “wave”. They are a series of fast-moving waves in the
ocean, usually caused by powerful earthquakes or volcanic eruptions. The
waves travel at great speed across the ocean with little energy loss. They
can remove sand from beaches, destroy trees, toss and drag vehicles,
damage houses and even destroy whole towns. Tsunami can also be
caused by meteorite impacts and undersea landslides. Tsunami are not
‘tidal waves’. Tidal waves are caused primarily by high winds pushing on
the ocean’s surface combined with a high tide.
An earthquake occurs out at sea
causing a volume of water to be
displaced upwards.
The displaced water creates a series
of fast moving waves (tsunami). As a
tsunami approaches, water will draw
back from the coast. If the slope of the
coast is not deep, the water may pull
back for hundreds of metres. People
who do not know of the danger will
often remain at the shore.
In the open ocean, a tsunami travels
fast (up to 900 kilometres per hour). In
shallow water its speed slows and its
wave height grows rapidly. Eventually
the wave breaks onto the coast and
may push water far inland.
1. Outline the origin of the word ‘tsunami’. 

2. Complete the table to show the differences between a tsunami and a tidal wave.
Causes of Tsunamis Causes of Tidal Waves
3. Describe two warning signs of an approaching tsunami:
(a) 
(b) 
How Tsunami Form
1
2
3

























































   240   241   242   243   244