Connecting Planetary Interiors

and Surfaces

Shaping Planetary Surfaces

Planetary surfaces share some similar features, but not all.

Impact craters

Volcanoes and lava flowsErosional features

Uplifted mountains

Rift valleys

Examples of geological surface features:

Terrestrial planet interiors have similar layers

All terrestrial planet interiors underwent “differentiation”

How do we know what’s inside the Earth? Have we been there?

How do we know what’s inside the Earth? Have we been there?

NO! Seismic waves are our probes of the Earth’s interior

Seismic waves

P waves: “primary”, “pressure”, or “push-pull”

S waves: “secondary”, “shear”, or “side-to-side”

P waves can penetrate the liquid outer core

S waves can’t

This science is called “seismology”

The waves bend as they move through changing densities

Which is the densest layer of the Earth’s interior?

A) Crust

B) Lithosphere

C) Mantle

D) Liquid core

E) Solid core

What causes geological activity?

HEAT

So where does the heat come from?

Accretion

Impacts bring kinetic energy

Differentiation

Gravitational potential energy is released as denser material sinks

Radioactive decay

Still heating the Earth’s interior today

How do planets lose that heat?

Radiation

Convection

Conduction

When a planet has lost too much heat, it loses its geological activity:

Volcanoes

Plate tectonics

Earthquakes

Large planets stay warm longer:

• More heat to begin with

• Smaller surface area to volume ratio

3 ways:

Note that convection can carry heat all the way out through the crust in the form of volcanoes

Magnetic Fields

Bar magnet –

field created by orbiting electrons

Electromagnet –

field created by electrical current

Earth’s magnetic field –

created by convection in molten core and Earth’s rotation

Magnetic field also depends on internal heat

All magnetic fields are created by moving charges

Volcanism

Wind erosion Impact cratering

Water erosion

Glacial erosion

Plate tectonics

Shaping planetary surfaces

Impact Cratering

The explosion is caused by energy

released (vaporizing the rock), like a bomb going off

The underlying crust is fractured

Ejecta is thrown out and may create

“secondary craters…”

Typical features in larger craters:• Central peak (rebound)

• Terraced walls

These features erode over time

Secondary

Craters

(and rays)

Ejecta

“blanket”

Only relatively young craters retain those features

Theophilus

Cyrillus

Catharina

Fracastorius

Mare Nectaris

Rosse

Madler

Rank the craters, oldest to youngest.

A) Ptolemy, Alphonsus, Arzachel

B) Ptolemy, Arzachel, Alphonsus

C) Arzachel, Alphonsus, Ptolemy

D) Arzachel, Ptolemy, Alphonsus

E) Alphonsus, Ptolemy, Arzachel

Alphonsus

Ptolemy

Arzachel

Volcanism

Low viscosity

Maria

Medium viscosity

Shield volcanoes

High viscosity

Stratovolcanoes

Silica content determines viscosity

Plate tectonics

Plate movement is driven by convection in the mantle

Crust

Oceanic crust: Denser, sinks below continental

Continental crust: Less dense, rides above oceanic

Mid-ocean ridge: New crust is forming here

Subduction: Where oceanic crust sinks below continental

Rift zone: Where continental plate is being pulled apart

Plate tectonics

Erosion

Sedimentary rock is the most common type on Earth’s surface

Erosion creates oxbow lakes

Which process formed the geological feature shown?

A) Impact cratering

B) Water erosion

C) Volcanism

D) Tectonics

E) Glacial erosion

Which process formed the geological feature shown?

A) Impact cratering

B) Water erosion

C) Volcanism

D) Tectonics

E) Glacial erosion

You can tell the relative age of surfaces by looking at the number of impact craters

Few craters = relatively young

(3.0 – 3.9 billion years)

Lots of craters = relatively old

(4.4 billion years)

Astro-Cash Cab!

Marissa Harmon

Josh Beardslee

Angelica Raya Trejo

Oliver Aitchison

Rodney Nelson

1) Which seismic waves travel faster?

P waves

S waves

They travel at the same speed

2) True or False?

Lunar maria were formed from high viscosity lava.

3) Which surface-shaping geological process requires an atmosphere?

4) Which terrestrial planet is more likely to have a strong magnetic field?

Small planet

Large planet

They would be equally likely