Chapter 17 The Dynamic Earth
17.1 Structure of the Earth:
The Earth is composed of layers
Crust - ____________________
That makes up continents and sea
The _________________ is the
region formed by the crust and the
outer layer of the ________
The _____________________ is
the fluid-like layer of mantle
beneath the lithosphere
•Scientists obtain information about the structure of Earth through __________ and
____________ observations.
Direct observations include _________________ directly from Earth’s interior.
Volcanoes – lava flows
-Rock samples
Indirect observations include ______________________________ differences around the globe to infer the
density of material beneath Earth’s surface.
Measuring of magnetic fields and gravity
Observations of how earthquake waves travel through the layers (next unit you will learn more on
Modern Mapping:
-satellite & ariel photos
-Infrared and radar images
At one time the continents formed ______________, A single huge landmass
DO CYU 17.1 p. 496 # 1-11
17.2 Evidence of a Dynamic Earth:
Continental Drift Theory: - The surface of the Earth
the following evidence
Puzzle fit of continents
Geological coastline matches
Fossil matching
First proposed by Wegner based on
Coal deposit matching
Equatorial glacial evidence
Unfortunately his theory was not accepted until when HOW the continents moved was better understood!
DO CYU 17.2 p. 500 #1-7
17.3 New Evidence of a Dynamic Earth:
occurs at mid-ocean ridges
when magma rises from the
mantle and _________ ___
the cracks left by the sea
floor moving apart
1. Mid-Ocean Ridges & Maps
Mid-oceanic ridges are __________________________________________
The sea floor is cycled back
into earth at __________
The discover of mid-ocean ridges where the sea floor was spreading, as well as trenches where continents and
oceanic plates met etc. were mapped along with known locations of high volcanic and earthquake history and this
showed the boundaries of the “plates” See Fig 1 p. 501
2. Sea-Floor Spreading
Heat within the Earth creates
_______________________ in the
mantle that help move the plates.
Radioactive dating of core samples
confirmed that the sea floor is older
Radioactive dating  When they looked at the mid-ocean ridges closer it was discovered that the rock was
youngest at the ridges, and oldest at the trenches where the oceanic plates dip under the continental plates
Magnetic Evidence there is also a pattern of magnetic shifts that can be observed moving away from the
divergent ocean ridges that show that new plate is forming and moving outward from both sides of this boundary. See
Fig 3. P. 503
17.4 Theory of Plate Tectonics:
The theory of plate tectonics states that the lithosphere is divided into ________ ________________ and
about __________ smaller ones.
The lithosphere is divided into 12 sections called plates plus 20 smaller ones. These tectonic plates “float” on top of the
dense fluid like asthenosphere which creates a push-and-pull on these plates due to large slow moving convection
current within it, causing many different plate boundary phenomena
The point where two plates move away from each other is
called a ___________ _________________.
________________, _________________, and
____________________ are created at this type o boundary
Plates moving towards each other collide at a
Plates move past each other in opposite directions at
____________________ and __________________
________________ are created along this type of
Summary of Plate Movement
Plate Boundary
Description of Movement
Geological Formations
Chapter 18 – Plate Tectonics
18.1 Causes and Effects of Plate Movement: Mantle Convection: see Fig 1p. 517
Shaping the Earth:
CYU 18.1 p. 521 #1-10
DO Worksheet with new seating partners
18.2: Geological Events:
Volcanoes: - mark cracks in the lithosphere where magma & gas reach the surface
Found at:
Mid-Ocean Ridges
Volcanic Belts -
Volcanic Island Arcs –
Hot Spots –
Earthquakes: - mark locations where transform boundaries form faults
***P waves travel faster (about 1.7x) than s waves
What do P-waves and S-Waves provide indirect evidence for?