Stable Earth

Question 1

What does a seismograph show?

Answer 1

A seismograph shows the different types of earthquake wave.

Question 2

L waves

Answer 2

L waves travel round the surface very slowly.

Question 3

P waves are longitudinal pressure waves:

Answer 3

• P waves travel through the Earth at between 5 km/s and 8 km/s
• P waves can pass through solids and liquids

Question 4

S waves are transverse waves:

Answer 4

• S waves travel through the Earth at between 3 km/s and 5.5 km/s
• S waves can only pass through solids.

Question 5

P waves travel through the Earth:

Answer 5

• They are refracted by the core
• The paths taken by P waves mean that scientists can work out the size of the Earth’s core.

Question 6

S waves are not detected on the opposite side of Earth to an earthquake:

Answer 6

• They will not travel through liquid
• This tells scientists that Earth’s core is liquid.

Question 7

What causes a tan?

Answer 7

• A tan is caused by the action of ultraviolet light on the skin.
• Cells in the skin produce melanin, a pigment that produces a tan.

Question 8

People with darker skin do not tan as easily…

Answer 8

because ultraviolet radiation is filtered out.

Question 9

How to reduce risk of sunburn?

Answer 9

• Use a sun screen with a high SPF, or sun protection factor, to reduce risks.
• maximum length of time to spend in the sun = published normal burn time × SPF

Question 10

Dangers of exposure to ultraviolet radiation

Answer 10

People are becoming more aware of the dangers of exposure to ultraviolet radiation, including the use of sun beds.

Question 11

Scientists and the Ozone layer.

Answer 11

• At first scientists did not believe there was thinning of the ozone layer – they thought their instruments were faulty but other scientists confirmed the results and increased confidence in the findings.
• Scientists monitor the thickness of the ozone layer using satellites.

Question 12

Where is Ozone found?

Answer 12

In the stratosphere.

Question 13

What does Ozone do?

Answer 13

• Ozone helps to filter out ultraviolet radiation

Question 14

CFCs

Answer 14

• CFC gases from aerosols and fridges destroy ozone and reduce the thickness of the ozone layer.
• This increases the potential danger to humans.
• The ozone layer is at its thinnest above the South Pole because ozone depleting chemicals work best in cold conditions.
• There is international agreement to reduce CFC emissions.