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Chapter 13: Problem 13

The letters following each Review Question refer to the corresponding Learning Objective from the Chapter Opener. What may have caused the Cretaceous flooding of the continents? (C)

Short Answer

Expert verified
The Cretaceous flooding of the continents may have been caused by a combination of factors, including: 1) a rise in sea level due to melting polar ice caps, changes in Earth's crust, and possible evaporation of water from the oceans, 2) changes in Earth's crust caused by high tectonic activity, leading to the formation of new ocean basins and the rearrangement of continents, and 3) climate change during the Cretaceous period, characterized by high humidity and precipitation, which increased rainfall and groundwater levels, leading to flooding of low-lying areas.

Step by step solution

01

Understand the Cretaceous Flooding

To answer this question, we need to know about the Cretaceous period and the events that could have caused flooding. The Cretaceous period was a geological period that lasted from about 145 to 66 million years ago. During this time, Earth experienced an event known as the Cretaceous flooding, which caused the continents to become partially submerged.
02

Identify Possible Causes of Flooding

There could be multiple factors that contributed to the Cretaceous flooding of continents. Let us consider the most probable ones: 1. Sea level change: One of the potential causes of flooding during the Cretaceous period could be the rise in sea level. Sea levels might have risen due to various factors such as the melting of polar ice caps, changes in Earth's crust, and possible evaporation of water from oceans. 2. Changes in Earth's crust: The Cretaceous period was characterized by high tectonic activity, which led to the formation of new ocean basins and the rearrangement of continents. This activity could have caused the continents to subside, allowing seawater to flow over them. 3. Climate change: The Cretaceous period experienced a warm climate with high humidity and precipitation, which could have contributed to the flooding events. Increased rainfall could have led to higher river flows and a rise in groundwater levels, which in turn could have resulted in flooding of low-lying areas.
03

Synthesize the Possible Causes

Based on these possible causes, the Cretaceous flooding of the continents is most likely the result of a combination of factors, including: 1. A rise in sea level due to the melting of polar ice caps, changes in Earth's crust, and possible evaporation of water from the oceans. 2. Changes in Earth's crust caused by high tectonic activity, leading to the formation of new ocean basins and the rearrangement of continents. 3. Climate change during the Cretaceous period, characterized by high humidity and precipitation, which increased rainfall and groundwater levels, leading to flooding of low-lying areas. In conclusion, the Cretaceous flooding of the continents may have been caused by a combination of factors, including sea level change, changes in Earth's crust, and climate change.

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Cretaceous Period Geology
The Cretaceous period, spanning roughly from 145 to 66 million years ago, was a dynamic era in Earth's geological history. Marked by the last flourish of dinosaurs before their extinction, the Cretaceous is also notable for significant geological events that shaped the planet's surface.

During this time, Earth's continents continued to drift apart, a process that began in the preceding Jurassic period. This drifting forged new ocean basins and altered global geography. The presence of shallow inland seas was a distinctive feature, indicating regions where the sea level was higher than today.

Fossil records from the Cretaceous reveal diverse marine life, indicating that seas encroached upon areas that are now land. Sedimentary rocks from this era, like limestone and chalk (famously exemplified by the White Cliffs of Dover), were deposited in these warm, shallow seas and provide evidence of past marine environments.
Sea Level Change
Sea level change is a critical factor in understanding the flooding of continents. During the Cretaceous, sea levels were significantly higher than present-day levels. There are a few key contributors to this rise:

  • The thermal expansion of seawater as a result of higher global temperatures.
  • Decreased polar ice volume, as the poles were much warmer and less ice-capped than today.
  • Tectonic processes that reshaped ocean basins, increasing their capacity and shifting water distribution.

These factors collectively led to a transgression of the seas over what would currently be considered coastal and inland areas, resulting in extensive flooding of the continents.
Tectonic Activity
Tectonic activity played a pivotal role in shaping the Earth's surface during the Cretaceous period. The movement and interaction of Earth's lithospheric plates led to dramatic changes in the planet's geography.

Rift Formation and Oceanic Expansion

Continents were pulled apart, creating rifts that eventually became oceanic basins. As these new basins formed and expanded, the continental plates became flooded due to the combination of subsidence and rising sea levels.

Mountain Building

Conversely, converging plates gave rise to mountain building, which is evident today in ranges such as the Rockies and the Andes. These geological processes not only influenced the distribution of water but also impacted climate patterns and the biosphere.
Climate Change during Cretaceous
Climate during the Cretaceous was warmer than the present day, with reduced temperature gradients from the equator to poles. This 'greenhouse climate' led to high levels of humidity and precipitation.

The increased rainfall could have contributed to the flooding in several ways:

  • Rivers carried more water and could have overflowed their banks more frequently, inundating adjacent lands.
  • The saturated ground may have been unable to absorb additional rainfall, leading to surface runoff and flooding.
  • Warm temperatures could enhance the hydrological cycle, thereby increasing the volume of water circulating through the atmosphere and falling as rain.

These climatic conditions, in conjunction with rising sea levels and tectonic shifts, created the perfect storm for widespread flooding during the Cretaceous period.

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Most popular questions from this chapter

The letters following each Review Question refer to the corresponding Learning Objective from the Chapter Opener. Did supercontinents exist in the Proterozoic? (F)

The letters following each Review Question refer to the corresponding Learning Objective from the Chapter Opener. How did the Alleghanian and Ancestral Rockies orogenies affect North America? (F)

The letters following each Review Question refer to the corresponding Learning Objective from the Chapter Opener. What life forms appeared during the Mesozoic? (E)

The letters following each Review Question refer to the corresponding Learning Objective from the Chapter Opener. During intervals of the Paleozoic, large areas of continents were submerged by shallow seas. Using Google Earth, tour North America from space. Do any present-day regions within North America consist of continental crust that was submerged by seawater? What about regions offshore? (Hint: Look at the region just east of Florida.) (E)

The letters following each Review Question refer to the corresponding Learning Objective from the Chapter Opener. Why are there no whole rocks on the Earth that yield isotopic dates older than about 4 billion years? (B)
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