TOP 81 GEOLOGY FACTS
1. Geology is the study of rocks. We study rocks to determine the history of the earth.
When you know history, you can predict the future.
2. Minerals are the main ingredient of rocks. Rocks are made up of 1 or more minerals.
3. There are about 3,000 minerals on Earth.
4. Minerals can be made up of one chemical or several chemicals. Examples of minerals
made of one chemical are copper, silver, gold, and diamond. Examples of minerals made
of more than one chemical are turquoise, hematite, topaz, salt, and quartz.
5. One type of mineral is a crystal, also known as a gemstone. Examples of crystals
include your birthstones: garnet, amethyst, bloodstone, diamond, emerald, alexandrite,
ruby, sardonyx, sapphire, tourmaline, citrine, and zircon (or turquoise or lapis lazuli).
NOTE: these are the traditional birthstones; some were changed in America in 1912.
6. Crystals take thousands of years to grow with the exception of salt (halite), which grows
so quickly you can watch it with your naked eye!
7. An object’s elevation is how far above or below it is when compared to sea level. For
example, the top of a mountain’s elevation is 4,000 miles above sea level.
8. There are three types of rocks. They are igneous, sedimentary, and metamorphic.
9. Igneous rocks come from the core of the earth. When magma or lava cools, it forms an
igneous rock. Examples of igneous rocks include pumice, quartz, and obsidian.
10. Sedimentary rocks are those that have settled at the bottom of a lake or ocean.
Examples of sedimentary rocks include shale, limestone, and sandstone.
11. Sedimentary rock covers 75% of the earth’s surface but only makes up 5% of the rocks
that make up the entire sphere of Earth. Fossils are most often found in sedimentary
rocks.
12. Weathering is the breaking down of rocks with the help of water, temperature,
chemicals, or wind on a landscape. Specifically speaking, weathering occurs when the
land is exposed to water, wind, and the freeze/thaw cycle.
13. Over time, dead plants and animals are covered with sediment. The carbon in the
plants and animals can be turned into coal, oil, natural gas, and petroleum based on the
amount of time, pressure, and temperature.
14. Metamorphic rocks are originally metamorphic, sedimentary or igneous rock that has
changed. Metamorphic rocks change when the earth’s crust moves, exposing rock to a lot
of heat and pressure. Metamorphic rock is the least common of the three types of rock.
15. When quartz, which is an igneous rock, is exposed to pressure and heat it turns into
quartzite, which is a metamorphic rock.
16. When shale is exposed to heat and pressure it turns into slate (so it goes from a
sedimentary rock to a metamorphic rock). Another example of sedimentary rock turning
into metamorphic rock is when limestone turns into marble.
17. When rocks break down into smaller and smaller pieces, they are referred to as sand.
18. When nutrients are added to sand, the sand turns into soil. Plants can grow in soil
because soil has nutrients such as nitrogen. The nitrogen is added to the sand when dead
plants and animals are decomposed, returning the nitrogen in their bodies to the ground.
19. Another name for soil is dirt.
20. The process by which rocks are created is called the Rock Cycle. The rock cycle is
similar to the water cycle but it requires much more time.
21. The rock cycle is just that – a cycle, which means there is no beginning or end.
22. Rock cycle: Sedimentary and igneous rocks that are exposed to heat and pressure will
turn into metamorphic rock.
23. Rock cycle: Metamorphic rock can either be uplifted to form mountains or can fall into
the earth’s core and become magma. Magma can turn into igneous rock if it is exposed to
a cool environment.
24. Rock cycle: Igneous rock can be exposed to erosion and cementation, causing it to
move and settle at the bottom of a body of water, making the rock now sedimentary rock.
25. The earth has four layers: crust, mantle, outer core, and inner core.
26. The earth’s crust is the outer layer of the earth’s surface. Under the ocean, the crust is
about 5 miles deep and under the continents the crust is about 25 miles deep.
27. The mantle is just below the crust. The mantle is about 1,800 miles thick. Some of the
mantle is so hot that the rocks here are liquid (molten rock). The temperatures range from
1,600 – 6,700 degrees Fahrenheit, depending on how close the area is to the core.
28. The outer core consists of liquid metal (iron and nickel) that creates the earth’s
magnetic field as the earth rotates on its axis.
29. The inner core is a solid mass of metal (iron and nickel). The inner and outer cores are
about 2,200 miles thick and are estimated at 13,000 degrees Fahrenheit.
30. The earth has 14 major tectonic plates and 38 minor tectonic plates. Tectonic plates
are the earth’s crust and upper portion of the mantle. Tectonic plates move 5-10 cm every
year, which is about the same rate that your fingernails grow.
31. When tectonic plates move, the earth’s crust experiences earthquakes, rift valleys,
mountains, faults, and erupting volcanoes.
32. Tectonic plates move both horizontally (right and left) and vertically (up and down).
33. The movement of tectonic plates is called Plate Tectonics (um…duh). The theory of
plate tectonics was introduced in the 1960s and has since been scientifically proven using
satellites in space. The two forces that cause plate tectonics are friction and gravity.
34. Divergent plate movement is when two tectonic plates in the ocean move away from
each other. During divergent plate movement, the magma from the earth’s mantle comes
through the space between the two plates, forming new crust. (ex: Hawaii)
35. Convergent plate movement is when two tectonic plates collide, crashing into each
other. There are three types of convergent plate movement.
36. One type of convergent plate movement is when both plates are located in the ocean.
One plate will push under another plate, causing magma to come to the surface, which
then creates a volcano.
37. One type of convergent plate movement is subduction, which is when one plate is in
the ocean and the other plate is from a continent. The continental plate is heavier than the
oceanic plate so the continental plate pushes down the oceanic plate. This causes
volcanoes, earthquakes, oceanic trenches, and tsunamis.
38. One type of convergent plate movement is when both plates are from a continent.
When they collide, mountains form because both plates will push the earth’s crust up. Ex:
the Himalaya Mountains
39. When tectonic plates move side by side (called transform plate movement), there is a
lot of shaking, also known as earthquakes.
40. Tectonic plates are also called lithospheric plates because they are located in the
earth’s lithosphere.
41. Topographic maps have contour lines that indicate an area’s elevation. They are also
called contour maps.
42. In 1915, Alfred Wegener, a German geologist, hypothesized that 200 million years ago
all the land on Earth was connected, making only one continent. He referred to the
continent as Pangaea, meaning “all-earth”. Plate tectonics broke Pangaea apart into the
continents we know today.
43. The lithosphere is the earth’s crust and upper portion of the mantle. It is in the
lithosphere that the tectonic plates are found.
44. The asthenosphere is the portion of the earth’s mantle that is under the lithosphere.
45. Convection is the movement of heat through liquid.
46. Convection causes the asthenosphere to move, which then causes friction between it
and the lithosphere. This friction causes the tectonic plates to move, which causes things
such as earthquakes, tsunamis, and the formation of volcanoes.
47. Magma in the asthenosphere moves because of convection. Magma at the top of the
asthenosphere cools and falls toward the bottom, near the core of the earth. As the
magma gets closer to the core, it warms up. Hot things rise so the magma begins to rise
toward the top again. But when it gets up there it’s farther from the core and begins to cool
off, causing it to fall toward the bottom of the asthenosphere again.
48. Magma is molten rock that is still under the surface of the earth.
49. Lava is magma that is now on the surface of the earth.
50. Rocks are classified into types. This classification occurs by observing and testing four
things: color, hardness, texture, and grain. However, rocks are ultimately classified based
on how they were created, not their physical characteristics.
51. Volcanism is the process by which magma and gases are transported from under the
earth’s crust to the top of the crust. The study of volcanoes is volcanology.
52. Deposition is the settlement of eroded rock and soil. Deposition generally occurs in
bodies of water as the water flow slows down. For example, if a river is flowing quickly it
will carry small rocks and soil. But when the river slows down, the water’s force is too small
to carry the rocks and soil so they fall to the bottom of the river.
53. Fossils are traces of organisms from past geologic times that have been preserved in
the earth’s crust. Fossils can include imprints in rocks, bite marks, preserved bones,
footprints, eggs, animal excrement (a rather nice term for poop), or nests and burrows.
54. Through the fossil and rock records scientists can determine what the earth was like
from its birth through today. This is how we create the geologic timeline.
55. The study of earthquakes is called seismology and the scientists are seismologists.
56. Earthquakes are measured based on both their magnitude and intensity.
57. Magnitude is the amount of energy released at the source of the earthquake, called
the focus. Magnitude is measured by a seismograph.
58. Intensity is the effect the earthquake had on the environment. Intensity is measured
by observing the damage caused by an earthquake. An earthquake that affects a large city
occupied by many people is going to be higher than an earthquake that occurs in the
middle of the ocean where there is nothing to damage.
59. The geologic timeline consists of eons, eras, periods, and epochs. You are probably
familiar with one period: the Jurassic Period.
60. The study of fossils is called paleontology.
61. Walter and Luis Alvarez theorized that a meteorite in Mexico killed the dinosaurs.
62. Erosion occurs when water, air, or ice moves rocks. EX: a landslide
63. Earth science is the study of the process by which rocks, fossils, soil, sediment,
landform, and water features are created. Earth science includes ecology, astronomy,
geology, seismology, volcanology, paleontology, chemistry, cartography, etc.
64. Topographic maps have contour lines and contour intervals.
65. Contour lines show a specific change in elevation.
66. The amount of elevation change is usually indicated in the map’s key and is referred to
as the contour interval. Every map has only one contour interval, or CI.
67. A constructive process is one that produces landforms.
68. A destructive process is one that destroys landforms.
69. Landforms are types of landscape such as a mountain, hill, river, valley, volcano,
delta, isthmus, ocean, peninsula, cliff and marsh.
70. Sea level is the ocean’s surface and is 0 km or 0 miles.
71. Evolution is the theory that organisms change over time because they are adapting to
environmental changes.
72. Adaptation is a change experienced by a single organism or an entire species. The
change helps the organism(s) survive.
73. Evolution DOES NOT state that monkeys changed into humans. Evolution states that
humans and chimpanzees have a common ancestor. The common ancestor has not yet
been found in fossils so it’s called the Missing Link because 1. it’s missing in the fossil
record and 2. it’s the link between humans and chimpanzees.
74. According to the fossil record, life began in Earth’s water. The fossil record leaves us
to believe that Earth was about 600,000,000 years old before it had water. And it was
about 3.4 bya when life first appeared on Earth. Scientists believe that life started out as
simple cyanobacteria called stromatolites, which were made up of only one cell
(unicellular). It took hundreds of millions of years before life became more complex and
grew to multicellular organisms.
75. Relative dating is when you compare two objects. There are no numbers involved in
relative dating. For example, Ms. Caswell is older than you.
76. Absolute dating is when you find out how old an object is. Absolute dating does
involve numbers. For example, Ms. Caswell is 67 years old.
77. When scientists look at a layer of rocks, generally speaking, the older rocks are on the
bottom and the younger rocks are on the top. Example: if you were standing at the bottom
of the Grand Canyon, the rock on the bottom where you are standing is older than the
rocks at the top of the Canyon where you began your hike.
78. Half-life is the time period it takes for half of a chemical to degrade to the point where
it’s changed into a different chemical. Example: Uranium-239 has a half-life of 23 minutes,
meaning that half of the atoms in a sample will change into neptunium-239 in 23 minutes.
79. The Ring of Fire is an area in the Pacific Ocean where the most volcanoes are found
and the most earthquakes occur.
80. Reliable data are data that can be trusted. You know it can be trusted because
there’s a pattern that you can use to predict the outcome of the next trial.
81. Valid data come from experiments that 1. match the test question to the experimental
design, 2. has only one independent variable, and 3. has data that answers the
experimental question (it’s a true cause and effect relationship).