16. Which of the following statements best explains the presence of seashell fossils in the Andes Mountains in South America?
Answer: C
The Andes Mountains were at one time under the Pacific Ocean and have since been pushed upward.
The presence of seashell fossils in the Andes Mountains can best be explained by the geological history of the region, which indicates that these mountains were once submerged under the Pacific Ocean. Over millions of years, tectonic activity caused these oceanic sediments, including seashells, to be uplifted into mountainous terrain.
A) While flying over the Andes Mountains, seagulls excreted the undigested remains of the shelled animals they had eaten.
This option is incorrect as it suggests an implausible mechanism for the presence of seashell fossils. The accumulation of fossils in mountain ranges is primarily due to geological processes rather than the activities of birds. Seagulls do not contribute to fossil formation in such a significant geological context.
B) The Andes Mountains are the highest in South America.
While this statement is true, it does not explain the presence of seashell fossils. The height of the Andes is a result of geological uplift, but it does not provide insight into the fossil record or the historical aquatic conditions that led to the fossilization of marine life.
C) The Andes Mountains were at one time under the Pacific Ocean and have since been pushed upward.
This statement accurately reflects the geological history of the Andes, highlighting that the mountains were formed by tectonic processes that uplifted land that was once part of the ocean floor. This uplift explains the presence of marine fossils, including seashells, found at high altitudes today.
D) Populations of marine invertebrates migrated out of the Pacific Ocean and into the Andes Mountains.
This option is incorrect as it implies an improbable migration of marine species to a mountainous region. Fossils represent organisms that lived in oceanic conditions, and their presence in the Andes is due to ancient geological processes rather than migration of species to high altitudes.
Conclusion
The correct answer, C, highlights the historical geological processes that explain the presence of seashell fossils in the Andes Mountains. Other options fail to account for the scientific understanding of how mountain ranges form and do not provide a logical explanation for the fossilization of marine life at such elevations. The uplift of formerly submerged oceanic regions definitively accounts for the fossil evidence found in the Andes.