th
8
Grade Science Final
Study Guide Review
I. Earth’s Layers
What are Earth’s Layers?
inner core, outer core, mantle and
crust
2. Which layer is the thickest?
the mantle
3. Which layers make up the tectonic
plates?
lithosphere – all of the crust and
the upper mantle
1.
II. Earth’s History
4. Who is Wegner?
The scientist who first came up with the
idea that the continents move, there was
once a super continent, Pangaea
5. Tell what supports his theory of
continental drift
Climate, similar rocks and fossils on
different continents
III. Boundaries/Tectonic Plates
6. Where is the crust oldest? How does this
support spreading centers? Boundary?
Older crusts will be found away from the
center, usually at trenches (convergent
boundaries).Younger rock at a ridge
(divergent boundaries)
7. Convection currents in the
asthenosphere?
As the hot molten rock moves in a current
in the asthenosphere it moves the plates in
the direction of the current
8. What is going on with the magnetic
minerals at the mid ocean ridges?
The minerals point in the same direction,
right now they are pointing north, over
time they will change direction. The pattern
is the same on either side of the ridge
9. Convergent Boundaries
 Colliding  
 Oceanic-Oceanic – two oceanic plates, the
older colder plate slides under the younger
plate – deep ocean trenches and volcanic
islands are formed
 Oceanic-Continental – the oceanic plate is
denser so it slides under the continental
plate – deep ocean trenches and coastal
volcanic mountains are formed
 Continental-Continental- continental crust
pushes together and mountains are formed
10. Divergent Boundaries
Plates are separating  
On the ocean floor mid ocean ridges will
be formed. When continents separate a
great rift valley will be formed
11. Transform boundaries
Plates scrape past one another.
When a lot of stress builds up an
earthquake will occur
IV. Earthquakes
12. What is an earthquake?
The release of stress built up due to the
sudden and quick movement of rocks along
a fault
13. What determines the strength of an
earthquake?
How deep the focus is and how far the
blocks of rocks move
14. Normal fault
Blocks of rock slide down as they pull apart
Divergent boundaries
15. Reverse fault
Blocks of rocks slide up as they push
against each other
Convergent boundaries
16 strike-slip fault
Blocks of rocks slide past each other
Transform boundaries
17.How many seismograms? Why?
THREE seismograms are needed, where
they intersect is the epicenter of the
earthquake
18. Difference between focus and epicenter
Epicenter is on earth’s surface which is
located directly above the focus. The focus
is the actual spot that the earthquake
occured
19. Primary waves, secondary waves, surface
waves
Primary waves- p-waves, move the fastest,
push pull, 1st to arrive at the seismograph
station, can travel through solid, liquid and gas
Secondary waves – s-waves, slower, move side
to side, second to arrive, can travel through
solids
Surface waves – move on the surface, cause
the most damage
20. Earthquake resistant buildings
Adding cross braces, moat and shear wall
V. Blocks of Rocks
21. Folded mountains
Occur at ancient boundaries when two
continental plates have collided
22. What causes blocks of rocks to tilt
along faults?
Spreading centers – like along the ocean
floor
VI. Volcanoes
23.Volcanoes
It is an opening through which lava, rocks
and gas erupt. Happen at convergent and
divergent boundaries and hot spots.
Three types – cinder cone, composite and
shield
24. Pyroclastic flow
The combination of very fast moving
extremely hot gases and rocks
25. What are the signs that a volcano may
erupt soon
Rising temperatures of local bodies of
water, increase gases, movement of rocks
26. Effects of a volcano
Effects: ash, lava, pyroclastic flow, rocks,
landslides, mudslides
Most dangerous: ash – ash clouds
Atmosphere: increased acid rain and a
decrease in temperature
VII. Rocks
27.Three types of rocks? contain/not contain
fossils
Sedimentary – different types of rocks, most
likely to contain fossils
Igneous – cooled molten rock, will not contain
fossils, will destroy fossils because of the high
temperature
Metamorphic – changing rock
28. Original remains/rock fossil
Original remains will be found in amber (sap
of a plant
Rock fossils are mold and casts
29. Rock layers
The youngest rock layer will be at the top,
igneous rock will be younger than the layers of
sediment it cuts through
30. Uniformitarianism
Earth is constantly changing and the same
forces that changes it in the past are changing
it today
31. Relative age/absolute age
Relative age – how the age relates to
something else, age of the layers of
sedimentary rock is determined this way
Absolute age – exact age based on facts, like
your age based on your birthdate
VII. Genetics and Heredity
32. What determines the genetic code?
The sequence of bases in a strand of DNA
33. What is the code for making RNA and
protein?
DNA
34. Where do you inherit your genes from?
Your parents
35. What is a genotype? Example
The traits that are passed down, includes
both alleles BB, Bb, bb
36. What is a phenotype? Example
The traits that are visible, how the alleles
combine, includes eye color, hair color,
earlobes
37. What are alleles?
Various forms of the same gene
38. What is the difference between
dominant and recessive genes?
Dominant is the gene that will show
through when paired with another
dominant or a recessive gene
DD
Dd
Recessive will only show when paired with
another recessive gene
dd
39. What is a Punnett Square? Ratio/percent
A diagram that will show the probability of
the traits of an offspring
T
T
t
100% chance of
Tt
Tt
genotype Tt
t
Tt
Tt
40. What is fertilization?
The process that takes place when a sperm
combines with an egg