Inside Earth: Chapter 1 Plate Tectonics

Section 1: Earth’s Interior

Quick Facts & Figures What if you could drive to the center of Earth? How long would the drive be? At 62 miles per hour: Half an hour to make it through most of the crust About an additional 29 hours to drive through most of the mantle Then an additional 35 hours to drive to the center of the core. 64.5 hours or about 2 ½ days! That’s about the time it would take to drive from here to Disney World.

Forces that change the surface: Constructive Forces: processes that help build up the Earth, either by depositing soil or silt in a river, or by volcanoes and lava flows that generates new land. Examples: Volcanic islands, sand dunes, river deltas Link Destructive Forces: processes that break down the Earth, either through the violent actions of volcanoes and earthquakes or by the steady flow of a river. Erosion, weathering, glaciers, volcanoes, earthquakes

Constructive vs Destructive Forces

What’s Inside? Scientists need to use both DIRECT and INDIRECT EVIDENCE Volcanic rocks, faults, erosion Experimental rocks, meteorites Indirect: Seismic waves, mass balancing, meteorites, orbital considerations Interactive link

Depth vs Pressure

S waves vs P waves

The Crust Includes soil, rock, mountains, and water Thinner than mantle & core areas Thinnest beneath the ocean; thickest under high mountains. Ranges from 5-40 km thick. Oceanic crust consists of dense rock like basalt Continental crust consists of less dense rock like granite. At some convergent boundaries, oceanic crust gets pulled under continental crust. This is called a subduction zone.

Granite vs. Basalt

The Mantle The uppermost part of the mantle and crust together form a rigid layer called the lithosphere. It averages about 100 km thick. Heat and pressure continue to increase making the area just below the lithosphere less rigid and flows slowly. The material is like soft road tar and bends like plastic. This layer is called the asthenosphere. Beneath the asthenosphere, solid mantle material extends to the Earth’s core. Mantle is nearly 3,000 km thick in all.

Asthenosphere vs Lithosphere

What about the mesosphere? Sometimes the part of the mantle between the asthenosphere and the outer core is referred to as the mesosphere. Don’t confuse it with the layer in the earth’s atmosphere between the stratosphere and the thermosphere…also called the mesosphere.

Prefixes can help… Asthenophere = astheno-, from Greek asthenēs “weak” Lithosphere = form of Greek lithos "stone“ Mesosphere = from Greek mesos 'middle'

The Core Consists of two parts: Outer core: Inner core: molten metal that surrounds the inner core Behaves like a thick liquid Inner core: Dense ball of solid metal Extreme pressure squeezes the atoms of iron and nickel so much they cannot spread out and become liquid Thickness = about 3,500 km Estimated temperature = about 2,000 C to 5,000 C (as hot as the sun’s surface!)

Earth’s Magnetic Field Currents in the liquid outer core force the solid inner core to spin at a slightly faster rate than the rest of the planet. This movement causes the planet to act like a giant bar magnet. The magnetic poles are NOT in the same location as the geographic poles. Link to more information Link to compass interactive Link to unitedstreaming clip