L2：
讲座
1. What is the main purpose of the lecture?
To explain how geologists determine the dates of ice ages
To compare the geologic features of several different ice ages
To discuss the possibility of a severe ice age during the Cryogenian period
To examine the effects of a Cryogenian ice age on subsequent climate patterns
2. Why does the professor discuss the name of the Cryogenian period?
To provide backgrounds for the basis of the Snowball Earth hypothesis
To suggest that the Snowball Earth hypothesis is inappropriately named
To contrast the Cryogenian period with later geologic periods
To point out that the Cryogenian ice ages started in several different ways
3. According to the professor, what factors might have created the conditions for a snowball Earth event?
A change in the proportion of land and wafer covering Earth’s surface.
The cooling effect of the oceans’ low surface albedo
A change in the atmosphere that lowered Earth’s surface temperature
A continuing cycle of radiation reflection and ice growth
4. Why does the professor talk about a research study in Oman?
To illustrate why it is necessary to study evidence of glaciers from more than one
location
To determine how solar radiation affects glaciation
To present evidence that Earth’s climate fluctuated during the Cryogenian period
To explain why ice ages during the Cryogenian period differed from other ice ages
5. According to the professor, what is the chemical index of alteration used for?
To describe changes in the chemical composition of the atmosphere
To measure the degree of chemical weathering of rocks
To find out how oceans affect global temperatures
To trace the movement of rock over time
6. What is the professor’s opinion about the Snowball Earth hypothesis?
Its basic premise is accurate and further study will validate it.
It would be more plausible if the time frame were longer.
It has some merit but a closer examination reveals flaws.
It will probably never be completely discredited.
