11.4

1. 1. Listen to Track 89.

      Now answer the questions.

   1. What is the lecture mainly about?

      1. Reasons that finding ancient rivers is important to the study of climate change
      2. A comparison of ancient and modern-day rivers in the Sahara Desert
      3. Satellite evidence of climate change in deserts
      4. A hypothesis for what the geology of the Sahara Desert was at one point in the past

   2. What is the professor’s opinion about the amount of plant growth in the modern Saharan climate?

      1. It will be crucial to monitoring the continuing climate change in the Sahara.
      2. It is abnormally bountiful considering the current climate.
      3. It explains the dry season that the Sahara is currently experiencing.
      4. It is limited, especially compared to growth during the African Humid Period.

   3. What factors could have contributed to the creation of the climates that existed during the African Humid Period? Choose 2 answers.

      1. The tilt of the Earth relative to the Sun
      2. The increase of greenhouse gases in the atmosphere
      3. The presence of water-dependent vegetation
      4. The drying of Lake Victoria

   4. What does the professor imply about the Southern Hemisphere during the African Humid Period?

      1. The level of greenhouse gases in the atmosphere was enough to increase the temperature in Southern Africa.
      2. The rivers in the Southern Hemisphere were larger and more common than they were in the Northern Hemisphere.
      3. The vegetation in the Southern Hemisphere was more varied at that time than it is today.
      4. Observation satellites have been unable to detect as many ancient rivers from that time period in the Southern Hemisphere.

   5. According to the professor, what was an observation satellite recently able to confirm?

      1. The degree of precipitation increase during the African Humid Period
      2. The presence of an ancient river in the Sahara Desert
      3. The position of ancient jungles relative to ancient rivers
      4. Differences in levels of greenhouse gases between the Northern and Southern Hemispheres

   6. What possible prediction does the professor give for the future of the 500 kilometer riverbed that was discovered?

      1. The riverbed could alter the area’s vegetation.
      2. The riverbed could itself bring about local climate change.
      3. The riverbed could start to flow again.
      4. A completely new riverbed could be carved in the Sahara Desert.