Analysis of the Earth and Environment Lecture 10: Geothermal & Radioactive decay

Question 1

Define one kilowatt hour

Answer 1

One kilowatt hour is 1000 watts (1000 joules/second) of energy used over a period of on hour.

1 kw (kilowatt) = 1000 joules per second

Question 2

Define Geothermal energy

Answer 2

Surface water and steam from hot springs/geysers

Heated water deep underground

Injection of water into hot rocks

Heat used directly in heating systems.

Question 3

Describe the pros of geothermal energy

Answer 3

-Little waste produced
-Very low Greenhouse emissions
-Reliable continuous supply of power (unlike wind or water)
-Small footprint

Question 4

Describe the cons of geothermal energy

Answer 4

-Does still bring up some green house gasses
-Can affect ground stability causing earthquakes
-Few suitable areas for exploitation
-Geothermal plants can run out of steam if exploited too rapidly

Question 5

Describe small scale geothermal plants: Ground source heat pumps

Answer 5

Heat extracted from solar energy stored underground to provide low temperature domestic heating.

Technically not geothermal energy as is just using stored solar energy in the earth.

Ground below 1m depth is at 8-12 degrees Celsius in the UK, even in winter.

Needs about 1KW of energy to produce 3-4KW heat energy.

Question 6

Define Radioactive decay

Answer 6

Radioactive decay is when a nucleus becomes unstable (due to particularly high or low number of neutrons - in relation to the number of protons)

The nucleus loses energy by radiation.

Question 7

Define Half life

Answer 7

The time it takes for half of the atoms of the nucleus(/half of the atoms still remaining) to undergo decay.

Question 8

What is the half life of carbon 14

Answer 8

Carbon 14 is an isotope of carbon which has 8 neutrons rather than 6, Thus making the nucleus unstable.

Carbon 14 is produced at a roughly constant rate in Earths atmosphere.

Half life is 5730 years. Meaning that half of the carbon 14 atoms in an object will have decayed in 5730 years.

Question 9

How are half lifes used to determine the age of something

Answer 9

Half lifes can be used to determine the age of the object through examining the amount of the decaying atom remaining in the object.

Question 10

Describe the two ways/isotopes that Uranium decays

Answer 10

Uranium-238 decays to Lead-206
With a half life of 4.5 Billion years

Uranium-235 decays to Lead- 207
With a half life of 700 million years

Uranium gradually decays into Lead. Uranium content decreases whilst Lead concentration increases.

Uranium - Lead dating is only possible with rocks that exclude lead when they are formed.