Inside the Planet: Rock Cycle and Structure of the Earth
I. Lithosphere: minerals and rocks
A. Types of rocks
1. Igneous:
Intrusive / Extrusive
Felsic / Mafic / Ultramafic
2. Sedimentary
3. Metamorphic
B. Rock Cycle
II. Structure of Earth
A. Core
Inner / Outer
B. Mantle
Lower / Upper / Uppermost
Asthenosphere
C. Crust
Continental / Oceanic
III. Lithospheric Plates
Isostacy
Lithosphere is composed of minerals:
Definition of “Mineral” : Naturally occurring, Inorganic substance with Unique chemical and crystalline
structure.
92% of crust is composed of Silicate minerals (silicon and oxygen).
A rock is a natural solid substance made up of minerals; rocks are classified by origin : 3 types
A. Types of Rocks
1. IGNEOUS : molten rock that has cooled and solidified
(molten rock is magma or lava)
INTRUSIVE : cools below surface; big crystals; coarse
EXTRUSIVE: cools at surface; fine-grained
(phtos of examples)
Mafic and felsic igneous rock
 Felsic: mostly felsic minerals : High in feldspar and silicate minerals
o Lighter; Less dense

Mafic: mostly mafic minerals : High in magnesium and iron
o Darker,Denser
Ultramafic: all mafic minerals
2. SEDIMENTARY: made up of sediments that have been compacted and cemented.
sediments: all solid particles transported by water, ice, wind, gravity
examples of sediments: mud, sand, shells, debris, dust, rock fragments
examples of sedimentary rocks: mudstone, sandstone, limestone, conglomerate, shale
Sediments accumulate in layers, therefore sedimentary rock has “strata”
(photos of mudstone, sandstone, limestone, conglomerate, strata)
3. METAMORPHIC: altered from original rock by heat, pressure or chemical activity; began as igneous,
sedimentary, or metamorphic rock
shale --> slate
slate --> schist
granite --> gneiss
limestone --> marble
(Photos of gneiss, schist, slate)
Rock Cycle (diagram and explanation of processes)
II. Structure of Earth : composed of layers: Core, Mantle, Crust
A. Core
Inner
5150 – 6370 km (below surface)
Solid iron
5400 – 9000 degrees F
Outer
2900 – 5150 km
Molten iron
B. Mantle
Lower mantle
very dense;
iron and magnesium
670 – 2900 km
Upper mantle
rigid at lower end
250 – 670 km
“plastic” toward crust: asthenosphere
70 - 250
Uppermost mantle
Rigid
“Moho” to 70 km
Mohorovičić discontinuity
Boundary between crust and mantle
Change in seismic waves here
C. Crust
continental : 25 miles thick
Lower mafic; upper felsic (granite)
Less dense
oceanic: 5-6 miles thick
Mafic (basalt)
More dense
Lithosphere = uppermost mantle and crust (rigid; ultramafic)
III. Lithospheric Plates
Lithosphere is divided into large plates.
Rigid plates “float” on the plastic asthenosphere, just deep enough to support their own weight: Isostacy
Isostatic adjustment of crust:
add weight (sediment, glacial ice): crust will sink
remove weight (erosion, glacial ice melts): crust will rebound