FORCES OF CHANGE Chapter 2 Section 2

THINK ABOUT CHANGE…  How has change happening around you influenced your life? How have changes you made within yourself impacted your surrounding environment and the people in that environment?

ESSENTIAL QUESTION AND OBJECTIVE  EQ: How have internal and external forces shaped Earth’s surface?  OBJ: I will be able to use geographic terms and tools to explain how Earth’s internal changes and external changes influence the character of places.

LAYERS OF EARTH ORGANIZER Layer of EarthDistance (miles)Temperature (Farenheit) Description

EARTH’S STRUCTURE  The Earth is composed of three main layers  Core: intensely hot, solid inner section of Earth  Mantle: Thick layer of hot dense rock  Crust: a rocky shell that makes up the Earth’s surface  At the very center of Earth is the superhot but solid inner core  Scientists believe that it is made up of iron and nickel under enormous pressure, and that a band of melted iron and nickel surround it, called the liquid core

EARTH’S STRUCTURE  Scientists theorize that 500 million years ago the planet looked completely different  Pangea – the gigantic supercontinent where our current continents originate from  The theory is that the continents were once joined and then slowly drifted apart, known as continental drift  Plate tectonics refers to all of the physical processes that create many of Earth’s physical features  Plates moving around formed Earth’s physical features—continents, oceans, volcanoes, mountains  When plates spread apart, magma, or molten rock, is pushed up from the mantle and ridges are formed

RECAP:  Which of Earth’s layers is between the crust and the outer core?  How much does the temperature change from the inner core to the outer core? From the outer core to the mantle?  What is the theory of continental drift?

INTERNAL FORCES OF CHANGE Colliding and Spreading Plates  Mountains are formed where giant continental plates collide  Himalaya mountain ranges in South Asia were pushed upward when Indian landmass drifted against Eurasia  Mountains can also form when a sea plate collides with a continental plate  Subduction: when the heavier sea plate dives beneath the lighter continental plate  The Andes mountains in South America formed over millions of years as a result of subduction when the Nazca plate slid under the South American plate  Accretion: pieces of Earth’s crust comes together slowly as the sea plates slide under the continental plate  Created underwater mountains and peaks  Causes continents to grow outward  Spreading: when sea plates pull apart and causes a rift that allows magma to arise Folds and Faults  Folds, or bends, are formed in layers of rock when moving plates squeeze Earth’s surface until it buckles  Plates may slide past each other creating cracks in the Earth’s crust called faults  San Andreas Fault in California  Sheet glaciers are flat, broad sheets or ice and cover most of Greenland and all of Antarctica  Mountain glaciers are located in high mountain valleys

RECAP  How are mountains formed?  How are volcanoes formed?  What is a fault?  What is a fold?

INTERNAL FORCES OF CHANGE Water Erosion  When springwater and rainwater flow downhill in streams, it cuts into the land and wears away soil and rock Soil Building  Soil is the product of thousands of years of weathering and biological activity  Weathering breaks rock into smaller pieces  Worms and other organisms help break down organic material and add nutrients to allow air and water  Five Factors influence soil formation  Climate  Topography  Geology  Biology  Time

WHAT IS A VOLCANO? VIDEO 1. What is the general structure of a volcano? 2. When do eruptions occur? 3. What are the downsides to volcanic eruptions? 4. What are the benefits of volcanoes and their eruptions? 5. What happens when volcanoes stop erupting?