English Language Questions for CLAT | QB Set 10

Milankovitch proposed in the early 20th century that ice ages were caused by variations in the Earth’s orbit around the Sun. Initially, this theory was considered untestable due to the lack of an accurate timeline of the ice ages that could be aligned with these orbital changes. However, a recent scientific discovery has provided a way to test this hypothesis by measuring the relative volumes of land ice over time.

This is achieved by analysing the ratio of two oxygen isotopes, oxygen-16 and oxygen-18, in ocean sediments. Normally, most oxygen in water is oxygen-16, but a small percentage is the heavier oxygen-18. During ice ages, the growth of continental ice sheets reduces the water returning to the oceans. Since oxygen-18 is less likely to evaporate, the remaining ocean water becomes enriched with this isotope. By examining the oxygen isotope ratios in the calcium carbonate shells of marine organisms found in ocean sediments, scientists can estimate how much land ice existed during different periods. A higher ratio of oxygen-18 to oxygen-16 indicates more land ice.

This method of using isotope ratios has two major advantages for studying shifts in Earth’s climate. First, the isotope record is globally consistent, showing little variation between different geographic locations. Second, it provides a more continuous record compared to land-based geological evidence. As a result, scientists can date these sedimentary records accurately using radiometric techniques, allowing them to construct a detailed timeline of ice ages. This precise chronology has revealed a pattern of ice ages occurring approximately every 100,000 years, supporting Milankovitch’s theory that variations in Earth’s orbit are closely linked to the timing of these ice ages.

1. What is the main idea of Milankovitch’s theory as proposed in the passage?
   a) Ice ages are caused by changes in Earth’s magnetic field.
   b) Ice ages result from volcanic activity.
   c) Ice ages are caused by variations in the Earth’s orbit around the Sun.
   d) Ice ages are influenced by ocean currents.
2. How do scientists measure past volumes of land ice according to the passage?
   a) By studying volcanic ash layers.
   b) By analysing oxygen isotope ratios in ocean sediments.
   c) By measuring changes in Earth’s magnetic field.
   d) By analysing fossil records.
3. What does a higher ratio of oxygen-18 to oxygen-16 in ocean sediments suggest?
   a) Less water evaporation from oceans.
   b) More land ice during that period.
   c) A higher global temperature.
   d) Increased tectonic activity.
4. What advantage does the isotope method offer over land-based geological evidence?
   a) It is easier to gather data.
   b) It provides a more consistent and continuous record.
   c) It focuses on volcanic activity.
   d) It shows regional variations more clearly.

5. What is the significance of the pattern revealed by the isotope data?
a) Ice ages occur approximately every 100,000 years.
b) Ice ages occur randomly without any pattern.
c) Ice ages happen every 50,000 years.
d) Ice ages are caused by tectonic shifts.