Unit 3Evidence of Evolution

Target 1

Calculate the age of Rock by evaluating evidence of movements of continental and oceanic crust, theory

of plate tectonics.

Organization of Earth’s layers

Components of the layers of the Earth

CRUST: 3-5 miles under the oceans- 25

miles Under continents. Mostly granite and silicates

What is Granite and Silicates?

Granite, coarse- or medium-grained intrusive igneous rock that is rich in quartz and feldspar; it is the most common plutonic rock of the Earth’s crust, forming by the cooling of magma (silicate melt) at depth.

Silicates: The vast majority of the minerals that make up the rocks of Earth's crust are silicate minerals. These include minerals such as quartz, feldspar,& mica,

Mantle: Divided into 3 sections:

Lithosphere: ~60 miles of rigid crust.Asthenosphere: ~430 miles of partially molten

Rock, deforms fluidlyLower Mantle: ~1800 miles , mostly silicates,

more rigid and firm due topressure

Outer Core: ~3200 miles, Mostly liquid Iron,

Nickle, and Sulfur

Inner Core: ~3960 miles, Rigid, firm, sphere of

solid Iron/Nickle alloy

Convection currents in Earth’s layers

• Geologists believe the molten rock deep within the earth circulates by convection currents.

• The rock is in a semi-liquid state and should behave like any other fluid, rising up from the bottom of the mantle after becoming hotter and less dense from the heat of the earth’s core.

• As the rock loses heat into the earth’s crust, it becomes relatively cooler and more dense, sinking back down to the core.

• These constantly circulating areas of hotter and cooler molten rock are thought to help heat the surface.

• Some geologists believe convection currents within the earth are a contributing cause of volcanoes, earthquakes and continental drift.

Convection Currents in Earth’s layers

Three major ways the Earth moves

Divergent plate movement

• In plate tectonics, a divergent boundary

or divergent plate boundary is a linear

feature that exists between two

tectonic plates that are moving

away from each other.

• Divergent boundaries within continents

initially produce rifts, which eventually

become rift valleys.

Convergent plate movement/Subduction

• A convergent plate boundary is a location where two tectonic plates are moving toward each other, often causing one plate to slide below the other (in a process known as subduction).

• The collision of tectonic plates can result in earthquakes, volcanoes, the formation of mountains, and other geological events.

Transform plate movement

Transform boundaries are

places where plates slide

sideways past each other.

At transform boundaries

lithosphere is neither created

nor destroyed.

Many transform boundaries are

found on the sea floor, where

they connect segments of

diverging mid-ocean ridges.

California's San Andreas fault is a transform boundary.

San Andreas FaultThe San Andreas Fault is a continental transform fault that extends roughly

1,200 kilometers through California. It forms the tectonic boundary

between the Pacific Plate and the North American Plate, and its motion is right-lateral strike-slip

There are many Plate Boundaries around the Earth• The location where two plates meet is called a plate

boundary.

• Plate boundaries are commonly associated with geological events such as earthquakes and the creation of topographic features such as mountains, volcanoes, mid-ocean ridges, and oceanic trenches.

Look how our Earth’s

land masses have migrated

due to Plate movements

• Directions of Plate tectonic movement

How to date rocks?

Understanding how the rocks on Earth have moved, we can date the rock by using fossils.Relative Dating (not dating your relative!)

Index Fossils• Index fossils are fossils used to define and identify geologic periods.

Index fossils must have a short vertical range, wide geographic distribution and rapid evolutionary trends

Which fossil, A, B, C or D could be used as an index fossil?

Radiometric dating to determine age of rock.

• Geologists use radiometric dating to estimate how long ago rocks formed, and to infer the ages of fossils contained within those rocks.

• The universe is full of naturally occurring radioactive elements.

• When molten rock cools, forming what are called igneous rocks, radioactive atoms are trapped inside.

• The predictability of radiometric dating gives the scientists a reliable tool to calculate the age of almost any fossil or rock sample.

Here are some of the isotopes ofElements that areused to calculate the age of rocks.