Plate tectonics and Geologic Dating

The geologic time scale

Timeline of earths history established by geologic dating methods

Types of geologic dating methods

Absolute/Radiometric dating and relative dating

Absolute dating

Determines how many years old something is using radiometric dating (ex carbon-14)

What does absolute dating measure?

Rates of radioactive decay in rocks, fossils, etc.

carbon dating

A method for determining the age of organic material based on the amount of carbon-14 in a sample

Relative dating

Determines if one thing is younger or older than another using the law of superposition, correlation, or index fossils

Law of superposition

Sediments are laid down in horizontal layers, forming solid masses of layered, sedimentary rock

Which layer of sedimentary rocks are the oldest?

The bottom layer

Which layer of sedimentary rocks are the youngest?

The top layer

What are fossils the same age as?

Generally, the rock layers in which they are found

Why are fossils generally the same age as the rock layers in which they are found?

Due to the fact, the layers of fossils were formed around the same time

Superposition and fossils

Animal remains are left along with the sediments that will turn into sedimentary rock

Are intrusions and faults younger or older than the layers they cut through

Younger

Correlation

Matching similar rock layers in different locations to see if they formed at the same time

Index fossils

Fossils from creatures that existed for a geologically short period of time and fossils from creatures that had a wide geographic distribution

How many layers is when fossils from creatures that exist existed for a short period of time

One layer

Half life

How long it takes for half of the sample to decay/change

1 half life

/2

2 half lives

/4

3 half lives

/8

4 half lives

/16

Earth layers from outer to inner

Crust, mantle, outer core, inner core

Tectonic plate boundaries

Where tectonic plates meet and touch

What are the three types of plate boundaries?

Divergent, convergent, and transform fault

Divergent plate boundaries

Plates move away from each other, magma fills up the gap and makes new land

What do divergent plate boundaries form?

Mid ocean ridges, rift valleys, volcanoes

Convergent plate boundaries

Plates move toward each other

Oceanic-oceanic (convergent plate boundary)

One oceanic plate goes under the other oceanic plate

What do Oceanic-oceanic boundaries create

Trenches and volcanoes

Oceanic-Continental (convergent plate boundary)

Oceanic plate goes under continental plate

What do Oceanic-Continental boundaries create

Trenches and volcanoes

Continental-continental (convergent plate boundary)

Continental plates crashing into each other, forcing land up

What do Continental-continental boundaries create

Mountains

Subduction

When a tectonic plate moves under another at a convergent boundary, plate sinks into mantle and magma rises to crust

Transform boundaries

Plates slide past each other in opposite directions or sideways

what type of boundary is the San Andreas fault?

Transform

Fault

A fracture in earths crust where there is rock movement

Earthquake

Occur when the rocks of the lithosphere break along a fault, mainly at plate boundaries

What are the three types of faults?

Normal, reverse, and strike slip

What type of fault is the San Andreas fault?

Strike-slip

Lithosphere

Earths surface

Asthenosphere

Upper layer of the mantle

Theory of Plate tectonics

Earths surface is broken into pieces that slowly move the upper layer of the mantle due to the convection currents

Clues of plate tectonics

Continents fit together like puzzle pieces, fossils match on continents now separated by oceans, rock layers and mountain ranges match up, glacial evidence

What initially causes tsunami’s to form

A tectonic plate shifts abruptly, causing an earthquake and displacing water

Second step of tsunamis forming

Waves are generated and move out in all directions across the ocean

Third step of tsunami’s forming

Waves compresses they enter shallow water they slow down and build and height

Last step of tsunamis forming

Wave height increases, currents intensify, the tsunami’s waves can strike with tremendous force without warning, becoming threats to life and property

Where are volcanoes mostly found at?

Plate margins

Ring of fire

The convergent and transform plate boundaries between the pacific plate and its surrounding plates creates a ring of volcanoes

What are volcanoes formed by?

Subduction and hotspots

Hotspots

Stationary magma plume

Stationary

Unmoving

As a stationary hotspot keeps releasing magma, what happens to the tectonic plates?

They continue to move

How are volcanoes formed in regards to hotspots

As the plate moves away from the hotspots and the hotspot keeps removing magma

What is good evidence for plate tectonics

Oldest volcanoes are the furthest away from the hotspot