Name Class Date Enrichment: Glaciation and Earth’s Movement Read the passage below. Use a separate sheet of paper to answer the questions that follow. Are you still or moving as your read this page? You may feel like you are sitting still, but you are actually moving through space. You are moving along with Earth as it revolves around the sun. The position of our planet relative to the sun plays a major role in defining Earth’s climate and seasons. A long-term, climatic pattern that relates to Earth’s movements is the formation of glaciers during glaciation. We are currently within the Pleistocene Ice Age, a period that began about 1.8 million years ago. An ice age is defined as a period in which polar ice caps are present and glaciation is occurring within mountainous regions. Within this ice age, there are predictable cycles of glacial advances and retreats called glacial periods. Over the last 550,000 years, there have been five major glacial periods lasting a total of around 100,000 years, with interglacial periods in between lasting a total of around 10,000 years. Scientists can attribute three variations in Earth’s movements to the cyclic nature of glacial periods. They are known as the Milankovitch Cycles, and they include changes in Earth’s eccentricity, axial tilt, and precession. The precession of Earth describes how our planet wobbles as it spins on its axis. It’s like the wobble of a spinning top as it slows down. We know Earth wobbles because the axis shifts from pointing toward Polaris (the North Star) to pointing toward the star Vega. When the axis points to Vega instead of Polaris, the Northern Hemisphere experiences winter, when Earth is farthest from the sun instead of when it is closest to the sun. This results in greater seasonal contrasts that lead to a cooler climate and the formation of glaciers. Precessions occur on predictable cycles lasting 23,000 years. Research and describe the remaining two components of Milankovitch Cycles: eccentricity and axial tilt. Create a table and include the following information: How long each cycle lasts (periodicity) A description of the cycle How glaciation is related to Earth’s position in a cycle You must cite at least three Internet references from reliable sources, such as .gov and .edu sites. Analyze and Interpret Data 1. Describe Patterns Describe how the tilt of Earth’s axis results in the seasons and how Earth’s distance from the sun at any given time relates to winter and summer in the Northern Hemisphere. 2. Explain Phenomena A greater seasonal contrast means that summers and winters can be hotter or colder than normal in a given area. Describe how this can lead to glacial advances and retreats (melting). Enrichment Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.