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TRANSCRIPT
Chapter 1 The Earth in Context
Essentials of Geology, 4th edition by Stephen Marshak © 2013 W.W. Norton & Company
PowerPoint slides prepared by Rick Oches, Professor of Geology & Environmental Sciences, Bentley University, Waltham, Massachusetts
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GEOL 100 (Planet Earth) Topic #4 - Journey to the Center of Earth
Based on slides prepared by:
Ronald L. Parker, Senior Geologist Fronterra Geosciences Denver, Colorado
Updated by:
Rick Oches, Professor of Geology & Environmental Sciences Bentley University, Waltham, Massachusetts Modified by Stephen Altaner (Univ. of Illinois)
Essentials of Geology, 4th edition, by Stephen Marshak © 2013, W. W. Norton ! Chapter 1: The Earth in Context!
Journey to Center of Earth (Earth’s Interior) Topic title based on 1864 science fiction book Journey to
the Center of the Earth by Jules Verne Professor takes nephew through Icelandic volcano
following volcanic tubes toward center of Earth; encounter prehistoric animals and natural hazards, eventually return to surface in Italian volcano, Stromboli
Essentials of Geology, 4th edition, by Stephen Marshak © 2013, W. W. Norton ! Chapter 1: The Earth in Context!
Geology 100 - Planet Earth Discussion has begun this week (Aug. 31 - Sept. 2) in 219
Davenport Hall. Read Chap. 1 and Introduction in Discussion Guide; bring Discussion Guide to all
Discussions.
For Students Who Recently Added GEOL 100 • If you missed Discussion this week, then contact your TA
immediately to arrange for another time. TA names and Discussion schedule are on Class Web site.
• Get syllabus from Prof. Altaner. • Before each Lecture, bring printed Lecture Note summary found at:
http://classes.geology.illinois.edu/15FallClass/geo100/ • For routine questions, look at FAQ file on Class Web site.
Grades only at Illinois Compass 2g Web Site: https://compass2g.illinois.edu/
Essentials of Geology, 4th edition, by Stephen Marshak © 2013, W. W. Norton ! Chapter 1: The Earth in Context!
Layers of Earth - 3 distinct layers
Crust Mantle Core
Essentials of Geology, 4th edition, by Stephen Marshak © 2013, W. W. Norton ! Chapter 1: The Earth in Context!
Crust - Outer Layer Two kinds of crust: continental and oceanic.
Continental crust underlies continents. Average thickness ~35 km, ranges from 20 - 70 km Silicic (granite) to intermediate in composition
Oceanic crust underlies ocean basins. Average thickness ~7 km Mafic (basalt) in composition Denser than continental crust
Fig. 1.15a
Essentials of Geology, 4th edition, by Stephen Marshak © 2013, W. W. Norton ! Chapter 1: The Earth in Context!
Mantle - Middle Layer Base of crust to 2,900 km Mostly solid ultramafic
rock (peridotite) Denser than oceanic crust
Chapter 1 The Earth in Context
Essentials of Geology, 4th edition by Stephen Marshak © 2013 W.W. Norton & Company
PowerPoint slides prepared by Rick Oches, Professor of Geology & Environmental Sciences, Bentley University, Waltham, Massachusetts
2
Essentials of Geology, 4th edition, by Stephen Marshak © 2013, W. W. Norton ! Chapter 1: The Earth in Context!
Iron/nickel metal alloy (mostly iron)
2,900 km depth to center of Earth (6,370 km)
Outer part = liquid, inner part = solid
Circulation in liquid part of core is source of Earth’s magnetic field (important for navigation and protection from damaging solar radiation)
Core - Inner Layer
Essentials of Geology, 4th edition, by Stephen Marshak © 2013, W. W. Norton ! Chapter 1: The Earth in Context!
Initially, Earth = homogeneous mixture of hot rock + metal Heating from meteorite collisions, pressure, and
radioactive decay. Stage 1 = After ~10 - 20 million years, Earth melted,
allowing heavy iron to sink to Earth’s center, segregation between metallic core + rocky outer layer (mantle + crust)
Formation of Earth’s Layers - Core
Geology at a Glance
Essentials of Geology, 4th edition, by Stephen Marshak © 2013, W. W. Norton ! Chapter 1: The Earth in Context!
Stage 2 = Formation of crust (segregation of lighter crust from mantle) was very gradual and through several mechanisms. Began ~4 b.y.a. and grew to present size. Discussed in more detail later (plate tectonics).
Forming Earth’s Layers - Crust, Mantle
Essentials of Geology, 4th edition, by Stephen Marshak © 2013, W. W. Norton ! Chapter 1: The Earth in Context!
Crust directly sampled, mantle occasionally, never core Study earthquake (EQ) waves transmitted through Earth.
Speed of EQ waves is related to density of Earth's layer.
Earth’s Layers - How Do We Know?
P-wave velocity (km/s)
Essentials of Geology, 4th edition, by Stephen Marshak © 2013, W. W. Norton ! Chapter 1: The Earth in Context!
Lab experiments at high temperature and pressure Study of meteorites
Earth’s Layers - How Do We Know?
Iron meteorite
Stony meteorite