Connecting Planetary Interiors and Surfaces Shaping Planetary Surfaces

Planetary surfaces share some similar features, but not all. Impact craters Volcanoes and lava flows Erosional 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?

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