英语口语课ppt 第四纪冰河时代资料

3.Climate Ice age has changed the distribution of global climatic zone, a lot of plant and animal species used to live in a warm climate had extinction.
fig1:At least five major ice ages have occurred throughout Earth’s history: the earliest was over 2 billion years ago, and the most recent one began approximately 3 million years ago and continues today (yes, we live in an ice age!).
As the last glacial period progressed leading up to the LGM, sea levels worldwide dropped as water became stored in the ice sheets covering the world’s continents. Sea levels went down about 164 feet (50 meters) in 1,000 years.
Flora and Fauna
• human activities researching
accelerate
extinction
The influence of quaternary ice age
1. Surface water
The existence of large ice sheets which formed in the late Cenozoic changed the distribution of the surface waters. Hydrosphere water mass in the land and make the global sea levels dropped by about 100 meters.
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Content
• Introduction of "ice age" and the time of the last glaciation
• Glacial climate and sea level
• Flora and Fauna • The influence of quaternary ice age
Flora and Fauna
• vegetation types：similarity • some mammals：extinction
Flora and Fauna
Mammoths • • • • largest elephant 8 tuns shaggy long hair lesves and grass
So, if all these ice melt, the global sea level will rise from 80 to 90 meters, many big cities in the world and lowlands will be submerged.
2.Global tectonic movement The thousands meters of ice sheets during the ice age make earth’s crust under great pressure and slowly went down. As the quaternary ice disappear, the earth's crust is slowly rising. This tectonic movement is still going on now.
The warmer portions of the globe also experienced a change in climate due to glaciation in that most of them became cooler but drier. For example rainforest cover in West Africa was reduced and replaced by tropical grasslands because of a lack of rain.
fig2:The congruent relationship between the changes of CO2 and the temperature
Glacial climate and sea level
Since 2 million years ago, Earth’s climate has undergone a significant and complex evolution. The global weather became hugely unstable during that time. It dramatically switch its warming to cooling and back again.
Introduction of "ice age" and the time of the last glaciation
What is an ice age?
• An ice age is a long interval of time when global temperatures are relatively cold and large areas of the Earth are covered by continental ice sheets and alpine glaciers. Within an ice age are multiple shorter-term periods of warmer temperatures when glaciers retreat and colder temperatures when glaciers advance .
When was the last ice glaciation?
• There has been a series of ice ages over the past million years or so. Sometimes this whole period is referred to as the ‘ice age’, although it has included many individual glacial periods that alternated, every hundred thousand years or so, with warm periods called interglacials. More accurately, the ‘last ice age’ refers to the most recent of these glacial episodes. The coldest part, when massive glaciers extended as far south as Britain, happened between 25,000 and 20,000 years ago; we call it the last glacial maximum.
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