100 t04 layers - university of illinois at...

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

1

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


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/


Layers of Earth - 3 distinct layers

 Crust  Mantle  Core


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


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


  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


  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


  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


  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)


  Lab experiments at high temperature and pressure   Study of meteorites

Earth’s Layers - How Do We Know?

Iron meteorite

Stony meteorite

100 t04 layers - university of illinois at...

Documents