Takes place in repeating cycles, i.e. Warm age followed by Ice age

1. Change in Climate Industrial era Knights 30 Year War Vikings • Takes place in repeating cycles, i.e. • Warm age followed by Ice age Average Warm Age Little Ice Age Years Years Graphic illustration of more recent warming and cooling cycles.

2. Volcano activity • A possible cause for the cooling of the earth due to large volumes of dust blown into the atmosphere that blocks out the sun’s rays. • Reduces solar radiation.

3. 2. Heating of the atmosphere • Tectonic plates led to changes in environments Example: Extinction in Gondwanaland (Clarens in the Free State) • A mild climate with plenty of water in large lake systems, to a hot, dry desert climate. • Warmer climate leads to change in environmental food chains.

4. Disease • Change in climate - influences presence of disease causing organisms in environments and their effect on the survival of other organisms. • Also theory of extraterrestrial viral and bacterial invasion

5. Extraterrestrial theories • Explosion of a stars • Influence on earth radiation levels and destroys ozone layer • May have influenced extinctions (no scientific proof as yet) • Meteorite / asteroid collisions with earth • Meteorite –Large rocklike mass that falls from outer space onto earth – larger than 1 km (Vredefort and Parys) • Asteroid –off course orbiting fragments of a failed planet in the Asteroid Belt between Mars & Jupiter • Meteor – small fragments, burn up in space, called shooting stars • Comet – revolves in elliptic orbit around the sun, has solid nucleus + gaseous tail • Gamma radiation – from dying stars

6. METEORITES • Meteors (shooting stars) burn and glow when they enter earth’s atmosphere. • Most disintegrate into ashes and debris. • Some remain intact, known as Meteorites, to create craters on earth. • Can destroy life forms by shutting off sunlight for months / years.

7. Meteorites and Extinction • Growing evidence that meteorites are responsible for some major mass extinctions. • Meteorites may have added the final blow to species that were already weakened by global temperature changes, etc.

8. What happened to Dinosaurs? Scientific evidence: • Meteorite impact melted rocks in 200km diameter crater near Mexico. • Sediments deposited by enormous tsunamis (tidal waves) along coastline. • Caused acid rain and severe global cooling. • 70% of known fossils, including dinosaurs, wiped out (65 Ma).

9. Impact in Gulf of Mexico Dinosaur extinction • 200 km diameter crater in Mexican Gulf (near Chicxulub) • Caused by 10km diameter meteorite impact of 65 million years ago. • Impact caused acid rain, ash that blocked out the sun for months, severe global cooling (nuclear winter). • Increase in atmospheric CO2,resulting in global warming, final blow to dinosaurs & many other Cretaceous species.

10. VREDEFORT DOME • Crater 10 km in diameter. • Impact speed of 10 – 15 km /sec. • 16 km into earth’s crust. • Blast of impact caused 70km3 of rock to be vapourised and to spread into the atmosphere. • Location:100 km South of Johannesburg between Vredefort and Parys.

11. 5 MAJOR EXTINCTIONS • End of Ordovician • End of Devonian • End of Permian • End of Triassic • End of Cretaceous Time line of each extinction? Which was the most severe? Which was the least severe? Which is most recent?

12. SIXTH EXTINCTION • The impact of man on earth – human overpopulation • Current rate of extinction of species estimated at three species / hour or about 30 000 species per year.

13. Global warming • The big melt down • Rising ocean levels as polar ice caps and glaciers melt • Increasing global temperatures • Change in seasonal patterns • More frequent occurrence of weather extremes e.g. increase in droughts & floods • Migration of disease vectors for malaria, bilharzia and cholera

14. Human influence on the drastic increase in extinction of species • Industrial activity • Pumping greenhouse gases into atmosphere • Climate change • Pollution • Change of large parts of natural environments into food-producing agricultural areas & living spaces due to overpopulation and widespread habitat destruction.

15. RECENT EXTINCTIONS • Bluebuck • Quagga • Many frog species • Near extinction of Bontebok and Sable Antelope • Many Cycad species • Some Proteas and bulbs. Kwagga

16. The modern climate is depicted by a question mark, reflecting the uncertainty of the future climate. If humans were not present on earth, the climate would likely cool off into an ice age, as it has many times in the past. However, humans are disrupting earth's carbon cycle by burning fossil fuels, and releasing greenhouse gases into the atmosphere. By the Hansen et al. (1988) "Scenario A," the climate could warm 7.2°F (4°C) by the year 2050 should a worst-case materialize Something to think about Human Impact Humans McLean, D. M., 1991, A climate change mammalian population collapse mechanism, in Kainlauri, E., Johansson, A., Kurki-Suonio, I., and Geshwiler, M., eds., Energy and Environment: Atlanta, Georgia, ASHRAE, p. 93-100. Conservation and controlling growth of human population is a must to prevent 6th extinction – that of mankind