8th Grade 1st Quarter Assessment Study Guide
From Chapter 3:
Earth Systems: Hydrosphere - all water on Earth, Geosphere - all rocks on and inside Earth,
Atmosphere - blanket of air surrounds the Earth, Biosphere - all plants and animals on Earth
2 main energy sources that drive the earth system = heat from the sun and heat flowing out of
earth’s interior as it cools
constructive force = forces that build up mountains and other land masses; volcanoes,
earthquakes and mountains
destructive force = forces that destroy and wear away landmasses; erosion and weathering
Order of layers of Earth: Crust (tectonic plates here), Mantle (convection currents occurs here),
Outer Core (liquid metal), Inner Core (solid metal)- we know this by direct evidence (drilling rock
samples) and indirect evidence (seismic waves from earthquakes)
Order of layers of Earth: Lithosphere (crust and upper mantle), Asthenosphere (solid rock that
flows), Mesosphere (lower mantle), Outer Core, Inner Core
Direct evidence of earth’s interior = drilling samples
Indirect evidence of earth’s interior = refraction and reflection of seismic waves (speed and
path of the wave changes as it travels through different materials)
Convection Currents – in the asthenosphere cause tectonic plates (lithosphere) to move.
together forming a supercontinent called Pangaea; warm rock is less dense and rises; cool rock
is more dense and sinks
3 types of heat transfer:
conduction – direct contact of 2 objects touching each other
convection - circulation of a fluid (warm rises, cool sinks)
radiation – transfer of heat through electromagnetic waves
Earth is approximately 4.6 billion years old
From Chapter 4:
Evidence of Pangaea - continents fit together like Puzzle, fossils of same organisms in different
parts of world, same rocks and minerals that match up and climate evidence (evidence that
continents use to be closer to the poles or colder climates but are now closer to the equator
and vice versa)
Process of Sea-Floor Spreading – based evidence gathered by sonar of the ocean floor
 Mid-ocean ridges are long chains of underwater mountains where magma
continually rises to create new ocean floor
 Rock near a mid-ocean ridge is warmer, less dense and younger
 Evidence = ocean materials (pillow lava), magnetic striping (reversals) that are the
same on each side of the ridge, drilling samples (younger rock found near ridge –
older found farther away from ridge)
Process of Subduction – older, cooler and more dense rock is recycled back into the mantle
when it collides with another plate; pulled down by gravity
 Deep ocean trench – location where subduction occurs
Theory of Plate Tectonics: – the lithosphere is broken into 7 major and 7 minor tectonic plates
that have moved over time and continue to move slowly at a constant rate
Ring of Fire - place where earthquakes and volcanoes happen frequently, surrounds the Pacific
plate
Types of Boundaries:
Convergent: 2 plates collide
Divergent: 2 plates pull apart
Transform: 2 plates slide past each other in opposite directions
From Chapter 5 (lesson 1)
Types of Stress:
Compression –force that squeezes rocks until they fold or break; occur at convergent
boundary; can cause folded mountains (C & C), subduction (C & O, O & O)
Tension – force that pulls on rocks and thins in the middle; occurs at divergent boundary ; can
cause rift valley (C & O) or sea floor spreading (O & O) at mid-ocean ridge,
Shearing –stress that pushes a rock in 2 opposite directions; occurs at a transform boundary; can
cause; earthquakes, ex. San Andreas fault in California (NA & Pacific plates)
Types of Faults:
Normal: hanging wall moves downward; occurs with tension force at a divergent boundary
Reverse: hanging wall moves upward; occurs with compression at a convergent boundary
Strike-Slip: two blocks slip past each other in opposite directions; occurs with shearing at a
transform boundary
Landforms:
Folded mountains: Appalachians, Himalayans, Alps; caused by compression forces ; consist of
anticlines (upward arches) and synclines (downward arches)
Fault block mountains: Rocky & Sierra Nevada Mountains; caused by tension forces that result in
a normal fault when the hanging wall slips down between 2 footwalls
Plateau: a large area of land elevated high above sea level caused by uplift forces