Hi all,
Here are the answers to the post About Tsunamis. If you find the link disappears - let me know in feedback!
Oh, and just so you know, I use Dictionary.com for most of my definitions but remember to take context into consideration!
Part A Vocabulary
| To trigger something | To start something | To sweep onto | To move steadily and strongly onto | ||
| To shift | To move position | To engulf | To cover completely | ||
| A landslide | A downward sliding of a mass of earth and/or rocks | To near | To get closer | ||
| To be thrust up | To be pushed up violently | To brake | To stop | ||
| The body of water | The huge volume of water in total | Onshore | On the land by the sea | ||
| The ripples | Little waves |
Part A Questions
How is an ocean wave caused ?
An ocean wave is caused by the effect
of wind on the surface of the sea.
What 3 things can cause a tsunami and
what makes it so different from an ordinary wave ?
A volcanic eruption, or a
landslide or an underwater earthquake.
A tsunami happens when a huge volume of
water, not just on the suface, but right down to the ocean floor, is
shifted in one sudden
violent motion.
Exactly what happens to the ocean bed
when an earthquake cracks the ocean floor ?
One side of the fault is thrust up.
What is the effect of this on the water
above it ?
It pushes up the whole body of water
above the fracture.
Describe the height and length of a
tsunami.
A tsunami has a small wave height and a
very long wave length, mid-ocean.
What 3 things happen as it reaches
land ?
The water onshore gets sucked back
'drawback) ; the shallow water on the shore acts as a brake,
slowing the front of the wave down ; the back of the wave is
still travelling fast so it rears up.
How is the wave described ?
A wall of water.
Does it break onshore ? If not,
what does it do ?
No it doesn't break onshore, instead, it sweeps onto land, engulfing
everything in its path.
Part B Vocabulary
| A slab | A broad, flat somewhat thick piece of stone, wood or other solid material | Saw-tooth | Having a zigzag profile similar to the teeth of a saw | |||
| Sheer | Perpendicular, very steep | To loom | To come into view in indistinct and enlarged form | |||
| A geological fault | A crack in the earth's crust caused by displacement of the two sides | A spring | A coiled wire | |||
| Sharp | Having angular lines |
Part B Questions
On what date did the tsunami being
described, take place ?
26th December 2004
Why was it of interest to scientists ?
It was such a big tsunami, they wanted
to understand how different the earthquake was that had caused it.
What was below the ship ?
A vast undersea chain of mountains.
How have these been formed and over how
many years ?
They have been pushed up over millions
of years through the action of two tectonic plates.
What did the scientists use to
investigate the seabed ?
Remote equipment.
What did they find first ?
A sheer vertical cliff with a sharp,
saw-teeth edge that was evidence of the formation of a recent fault.
What did they discover next ?
A second, bigger cliff above the first.
What did this give evidence of ?
A megathrust earthquake.
What is the magnitude of this kind of
earthquake ?
Always over 9.
Why did it happen on this particular
date ?
After hundreds of years of the plates
pushing together, the pressure that had built up reached breaking
point on that day.
Hope you did OK!
Bye...until the next post!
