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Slide 1

Geology of Puerto RicoAn Overview of the Plate Tectonic

Origin of the Caribbean

Slide 2

Outline

• Rock types in Puerto Rico

• Plate Tectonics review

• Puerto Rico formed WHERE?

• Evidence

• Tectonic Reconstruction

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Slide 3

Rocks for Astronomers

Astronomy: H,He Metals

Geology: Basalt Other

Puerto Rico Volcanic Marine

Olivine Limestone

Mg2SiO4 CaCO3

Slide 4

Astronomy (simplified)

• Hydrogen

• Helium

• Metals (everything else)

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Slide 5

Astronomy Geology Rocks

• Hydrogen

• Helium

• Metal

(everything else)

• Hot (igneous)

• Medium (metamorphic)

• Cold (sedimentary)

Slide 6

Geology (continued)

• Hot = Igneous - Volcanic rocks, basalt– Lava is molten on the surface, cools quickly– Granite is molten underground, cools slowly

• Medium = metamorphic– Re-heating of rocks, re-crystalization– Cooking of limestone makes marble

• Cold = sedimentary– Carried by wind or water, like sandstone– Layered sands from dunes near the shore ( look along

the Jobos beach road cut)

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Slide 7

Basalt flow in Hawaii

Slide 8

Puerto Rico Geologic Map

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Slide 9

Puerto Rico Geologic Regions

Slide 10

Puerto Rico faults and intrusions

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Slide 11

Geology Field Trip

• Let’s look at a nearby outcrop of limestone

• (How often have you had an astronomy field trip?)

Slide 12

Limestone Fossils

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Slide 13

More Fossils

Slide 14

Structure of the Earth

• Earthquakes tell us about the interior structure

• Earthquakes generate P-waves and S-waves• P-waves are pressure waves – in direction

of motion• S-waves are shear waves – perpendicular to

the direction of motion • S-waves do not propagate through liquids

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Slide 15 Fig. 6-7, p.101

Slide 16

Seismology:a way to probe the Earth’s interior

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Slide 17

Global Tectonic Plates and Earthquakes

Slide 18

Plate Tectonics Overview

• Earth surface is made up of semi-rigid “plates” (lithosphere)

• The plates move on top of a plastic layer of rock (aesthenosphere)

• The driving force is convection in the mantle

• Heat from the core fuels the system

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Slide 19 Fig. 6-3, p.98

Slide 20

Types of Plate Boundaries

• Divergent – Spreading ridge (Atlantic)

• Convergent – Subduction Zone (Lesser Antilles, Pacific Rim)

• Neither - Transverse fault (San Andreas Fault, Puerto Rican trench at present)

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Slide 21

Global Tectonic Plates

Slide 22

Island Arc formation at a Subduction Zone

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Slide 23

Monserrat VolcanoSoufriére Hills

Slide 24

Before After

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Slide 25

Subduction of a spreading center

•Subduction cut off

•New trench forms on the other side

•Same volcanos may be activated

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Slide 27

Caribbean Plate Todayboundary and geologic regions

Slide 28

Tectonic Setting

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Slide 30

Plate Tectonic Reconstruction of the Caribbean region:

200 million years ago to present

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Slide 45

Caribbean Plate Todayboundary and geologic regions

Slide 46

Puerto Rico and Virgin Islands microplate