Ice Ages

1. Ice Ages Effects on Climate, Weather, & Geography

2. Ice Age • Referring to a long period of time in the reduction of earth’s surface & atmospheric temperature • Expansion of continental icesheets & polar ice

3. Large & Small Events • We’ve had at least 4 large ice age periods & dozens of smaller events. • The last ice age was approx 2.5 MYA • Advancing & retreating ice sheets (glacial) generally occurs in cycles every 40,000 to 100,000 years

4. Advancing & Retreating Ice • Glacial is advancing ice • Interglacial is retreating ice • The last glacial period ended 10,000 years ago

5. Glacial Period • Generally cooler drier climate over much of the earth • Sea levels are lower due to water retained as ice

6. Interglacial Period • Earth has been in an interglacial period for > 10,000 years • Climate warms

7. Glaciers form in places where the air temperature never gets warm enough to completely melt the snow.  Over the years, the snow becomes deeper as new snow falls.

8. Causes of Ice Ages • Several factors including: alignment of the planets / tilt of the earth / sun’s gravitational pull on earth / wobble (spin of the earth – because it is not completely round) • Climate patterns influence glaciations, including oceancurrents. • All of this effects weather – which is different from climate

9. On a 42,000 year cycle, the earth wobbles and the angle of the axis, with respect to the plane of revolution around the sun, varies between 22.1 – 24.5 degrees

10. Earth’s Wobble • Less of an angle than our current 23.45° means less seasonal differences between the Northern and Southern Hemispheres while a greater angle means greater seasonal differences (i.e. a warmer summer and cooler winter).

11. Climate & Weather • Climate is a given tolerance of temperature & moisture in specific region of earth measured over a given period of time. • Weather is the day to day effects of temperature / moisture in a given area. • Weather changes daily. Climate is a broad range of temp & moisture over a long period of time, with changes occurring slowly.

12. Ice Age Meltdown – 20,000 YA • Much of the Northern Hemisphere was covered by ice sheets. • Threatened the survival of all living things, including H. sapiens.

13. Ocean Currents & Climate Change • Ocean currents are a primary source of climate (heat / cold / moisture) around the planet • There is an “ocean conveyor belt” of cold & warm water flow (current) within the oceans around the world. • {warm water rises / cold water sinks AND fresh water rises / salt water sinks}

14. During the Meltdown of the last Ice Age • Fresh cold water runoff poured into the ocean • Instead of sinking, the fresh water (ice) is lighter & stayed on ocean surface – preventing the ocean conveyor system • Atmospheric Temp dropped 12 degrees in 20 years & created a mini-ice age {Younger Dryas event}

15. Repeat Event • This event occurred approx 6 times between 18,000 – 8000 years ago, with repeated climate shifts around the world. • All living things needed to quickly adapt to a constant changing climate

16. Climate Change – Geography Change • Glacial ice from the last ice age was up to 2 miles thick • 25 % of the planet was covered in ice • Lower sea levels showed land bridges between Siberia & Alaska / land between France & England / Florida was much wider • When the ice melted – runoff created enormous lakes / valleys / erosion of hill sides and numerous geographic changes - 60,000 trillion tons of water covered more of the earth than before the ice age • Sea level rose several hundred feet

17. Today • Temperature has risen 10 degrees overall since the last ice age • Sea level has risen 1 foot every century • We are in a global warming trend – not the *“man-made” global warming {*pollution} • With the addition of pollution {green house gases-CO2}, melting ice caps can change ocean currents & climate patterns – creating another ice age sooner than the natural cycle of change

18. The Future Before and after projection of parts of Spain due to global warming.