Plate tectonics states the earth's crust is broken into plates which can move.

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Millions of
Years Ago
Three main types of plate boundaries: convergent, divergent and transform.
Divergent Boundary
Convergent Boundary
Transform Boundary
Mountains form by uplift.
The half-life of a radioactive element can't be changed.

The diagram above represents a cube of radioactive material (Figure A) cut into eight identical cubes (Figure B).
Half-life of both samples are the same since you cannot change an elements half-life.

Index fossils are good time markers (widely spread, lived a short time).

Notice that this type of fossil is found over a wide area and (not shown) was short lived

Undisturbed strata - bottom layer is oldest.
Intrusion and faults are younger than the rock they are in.
Uranium 238 (U 238) dates old rocks.
Half life for U 238 is
4.5 x 10 9 years
Carbon 14 dates recent living objects.
Use your Earth Science Reference Tables! This is one of the most important tools in your test taking arsenal.

<1-10> <11-20> <21-30> <31-40> <41-50> <51-60> <61-70> <71-80> < 81-90> <91-100> <Test Taking Tips>

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