By the time you have completed the 3.15. Introduction & Exploration Activities, you should be able to:
Understand the meaning of the following terms/concepts and be able to identify examples of each: convection, tectonic plate, ocean basins, continents, tectonic plate boundaries, mountain belt, volcanic province, earthquakes, supercontinent, climate, greenhouse gas, greenhouse effect, weathering, Precambrian, Phanerozoic—Paleozoic, Mesozoic, Cenozoic.
Briefly describe how each of the following types of Earth change occurs: tectonic change, sea level change, climate change, surface change, biological change, and impact change. Also, understand that these types of change are interrelated (e.g., tectonic or biological change can cause sea level or surface change).
Understand that the normal state for Earth is constant change.
Answer: Convection within the earth is the slow flow of solid rock in Earth’s mantle. Earth’s mantle convects because cooling solid rock near the surface becomes denser and sinks into Earth. The upward flow of hot low-density rock balances this downward flow.
Convection within the earth is the slow flow of solid rock in Earth’s mantle. Earth’s mantle convects because cooling solid rock near the surface becomes denser and sinks into Earth. The upward flow of hot low-density rock balances this downward flow.
Example:
Answer:Convection produces the tectonic changes that generate earthquakes, volcanoes, ocean basins, and continents.
Convection produces the tectonic changes that generate earthquakes, volcanoes, ocean basins, and continents.
Term:
Tectonic Plate
Definition:
Answer: Earth’s uppermost rigid layer (lithosphere) consists of tectonic plates that meet along narrow plate boundaries, where plates converge, diverge, or slide sideways past each other.
Earth’s uppermost rigid layer (lithosphere) consists of tectonic plates that meet along narrow plate boundaries, where plates converge, diverge, or slide sideways past each other.
Example:
Answer:This image shows the major tectonic plates of the earth.
This image shows the major tectonic plates of the earth.
Term:
Ocean Basins
Definition:
Answer: Ocean basins are the area on the earth that are below sea level and covered with sea water.
Ocean basins are the area on the earth that are below sea level and covered with sea water.
Example:
Answer:Tectonic plates contain denser crust that forms ocean basins.
Tectonic plates contain denser crust that forms ocean basins.
Term:
Continents
Definition:
Answer: Continents are large land masses.
Continents are large land masses.
Example:
Answer: Currently the earth is divided into 7 large landmasses, or continents. They are Asia, Africa, North America, South America, Antarctica, Europe, and Australia.
Currently the earth is divided into 7 large landmasses, or continents. They are Asia, Africa, North America, South America, Antarctica, Europe, and Australia.
Term:
Tectonic Plate Boundaries
Definition:
Answer:The tectonic plate boundaries are the lines that separate the different tectonic plates.
The tectonic plate boundaries are the lines that separate the different tectonic plates.
Example:
Answer: This image from the reading shows a great example of the boundaries between tectonic plates.
This image from the reading shows a great example of the boundaries between tectonic plates.
Term:
Mountain Belt
Definition:
Answer: Tectonic plates move several inches each year. These movements produce uplifted bands of crust called mountain belts.
Tectonic plates move several inches each year. These movements produce uplifted bands of crust called mountain belts.
Example:
Answer: The Rocky Mountains in North America and the Alps in Europe are great examples of Mountain Belts.
The Rocky Mountains in North America and the Alps in Europe are great examples of Mountain Belts.
Term:
Volcanic Province
Definition:
Answer: Volcanic provinces are where voluminous magma erupts during the formation of mountains.
Volcanic provinces are where voluminous magma erupts during the formation of mountains.
Example:
Answer: Examples of volcanic provinces would be anywhere where eruptions took place during formation. An example would be the east coast of The United States.
Examples of volcanic provinces would be anywhere where eruptions took place during formation. An example would be the east coast of The United States.
Term:
Earthquakes
Definition:
Answer: Movement at plate boundaries are mostly episodic. When movement occurs it shakes Earth in events called earthquakes.
Movement at plate boundaries are mostly episodic. When movement occurs it shakes Earth in events called earthquakes.
Example:
Answer: This image shows places likely to experience earthquakes based on tectonic boundaries.
This image shows places likely to experience earthquakes based on tectonic boundaries.
Term:
Supercontinent
Definition:
Answer:Plate motions can both split and merge continents. Over long periods of time, continental mergers form supercontinents.
Plate motions can both split and merge continents. Over long periods of time, continental mergers form supercontinents.
Example:
Answer: Pangaea and Rodinia are examples of supercontinents.
Pangaea and Rodinia are examples of supercontinents.
Term:
Climate
Definition:
Answer: Climate is long-term average weather and can be characterized by attributes like temperature and precipitation.
Climate is long-term average weather and can be characterized by attributes like temperatureand precipitation.
Example:
Answer: A tropical climate is a climate where the annual temperatures are warm. A dry climate is a climate where there is little precipitation. These are just two oversimplified examples of climate.
A tropical climate is a climate where the annual temperatures are warm. A dry climate is a climate where there is little precipitation. These are just two oversimplified examples of climate.
Term:
Greenhouse Gas
Definition:
Answer: Greenhouse gases are near-surface atmospheric molecules.
Greenhouse gases are near-surface atmospheric molecules.
Example:
Answer: Common greenhouse gasses are carbon dioxide, water vapor, methane, ozone and nitrous oxide.
Common greenhouse gasses are carbon dioxide, water vapor, methane, ozone and nitrous oxide.
Term:
Greenhouse Effect
Definition:
Answer: Greenhouse gases can warm Earth’s surface by trapping energy, a process referred to as the greenhouse effect.
Greenhouse gases can warm Earth’s surface by trapping energy, a process referred to as the greenhouse effect.
Example:
Answer: The most common example of the greenhouse effect is the heat you feel in your car on a sunny day when you are inside with the doors and windows closed.
The most common example of the greenhouse effect is the heat you feel in your car on a sunny day when you are inside with the doors and windows closed.
Term:
Weathering
Definition:
Answer: Weathering is a process that breaks down rock. This is usually caused by exposure to the atmosphere (wind) or contact with water.
Weathering is a process that breaks down rock. This is usually caused by exposure to the atmosphere (wind) or contact with water.
Example:
Answer:Weathering can cause rocks to reshape in interesting ways.
Weathering can cause rocks to reshape in interesting ways.
Term:
Precambrian
Definition:
Answer: The Precambrian is a time period about 4,000 million years ago to about 540 million years ago.
The Precambrian is a time period about 4,000 million years ago to about 540 million years ago.
Example:
Answer:In the Precambrian eon single-celled life thrived, modern plate tectonics developed, oxygen levels in Earth’s atmosphere rose to roughly modern levels and animals emerged.
In the Precambrian eon single-celled life thrived, modern plate tectonics developed, oxygen levels in Earth’s atmosphere rose to roughly modern levels and animals emerged.
Term:
Phanerozoic
Definition:
Answer:Together, the Paleozoic,Mesozoic and Cenozoic form the Phanerozoic eon. The Phanerozoic eon is from about 540 million years ago to today.
Together,the Paleozoic, Mesozoic and Cenozoic form the Phanerozoic eon. The Phanerozoic eon is from about 540 million years ago to today.
Example:
Answer: The Phanerozoic is when most animal and plant life has existed on the earth.
The Phanerozoic is when most animal and plant life has existed on the earth.
Term:
Paleozoic
Definition:
Answer: The Paleozoic era was from about 540 million years ago to about 250 million years ago.
The Paleozoic era was from about 540 million years ago to about 250 million years ago.
Example:
Answer: During the Paleozoic eraEarth had a modern atmosphere and animals and plants flourished.
During the Paleozoic eraEarth had a modern atmosphere and animals and plants flourished.
Term:
Mesozoic
Definition:
Answer: The Mesozoic era was from about 250 million years ago to about 66 million years ago.
The Mesozoic era was from about 250 million years ago to about 66 million years ago.
Example:
Answer: In the mostly warm Mesozoic era mammals, dinosaurs, flying reptiles and flowering plants developed.
In the mostly warm Mesozoic era mammals, dinosaurs, flying reptiles and flowering plants developed.
Term:
Cenozoic
Definition:
Answer: The Cenozoic era is the current era we live in. It began about 66 million years ago.
The Cenozoic era is the current era we live in. It began about 66 million years ago.
Example:
Answer: During the Cenozoic mammals diversified and thrived; primates, grasses, and hominins (bipedal primates) developed; and Earth’s climate transitioned from warm to cool.
During the Cenozoic mammals diversified and thrived; primates, grasses, and hominins (bipedal primates) developed; and Earth’s climate transitioned from warm to cool.
Earth Changes
Thus far, we have explored Earth history using The Earth Timeline and a virtual field trip. In the final section of this Exploration Activity, we provide you with an opportunity to consider the types and magnitude of change that have occurred since Earth formed. We do this by posing and answering a series of questions focused on specific types of Earth change. For each, we list the type of change (for example, tectonic, sea level, biological change, …) and ask you to consider whether that type of change occurred in the area near BYU-Idaho.
Tectonic Change. Has the area where BYU-Idaho resides ever been covered by volcanoes or mountain belts?
Answer
Yes, the area has been volcanically active (and inactive) many times; in addition, mountain belts have formed and been eroded many times! These events in Earth’s past are recorded by volcanic rock bodies such as those recently produced by the Yellowstone supervolcano and Snake River Plain volcanoes (like those at Craters of the Moon) and by evidence for the erosion of many miles of rock, as discussed above. The image below shows Earth when the BYUI areas was mountainous and volcanically active.
Tectonic Change. Has the area where BYU-Idaho resides ever been part of a supercontinent?
Answer
Yes, at least 5 times! The most recent supercontinent was Pangaea. It began separating about 250 mya. As North America was separating from Eurasia and South America to the east, rock bodies such as the Chugwater Formation were forming in the west. The images below show the two most recent supercontinents—Pangaea and Pannotia
Climate Change. Has the area where BYU-Idaho resides ever been covered by thick glacial ice?
Answer
Yes, many times, during at least 3 separate ice ages. As we mentioned above, the most recent glacial ice in the area melted about 12,000 years ago. These events in Earth’s past are recorded by rock bodies such as the glacial deposits near Pinedale, Wyoming. The images below show the most recent period of glacial advance and an early period of extreme glaciation (so-called Snowball Earth glaciation).
Climate Change. Has the area where BYU-Idaho resides ever been covered by an unbreathable atmosphere?
Answer
Yes, for the first 86% of Earth’s history! This long period of Earth’s past is recorded by rock bodies like the oldest sedimentary rocks we observed on our trip. The image below shows Earth’s oxygen history and includes a photo of Venus, which has an atmosphere like early Earth.
Surface Change. Has the area where BYU-Idaho resides ever been covered by a huge sandy desert like the Sahara?
Answer
Yes, several times. These events in Earth’s past are recorded by rock bodies such as the Tensleep Sandstone. The image below shows a later sand sea.
Surface/Sea Level Change. Has the area where BYU-Idaho resides ever been at a shoreline or very near one?
Answer
Yes, many times! These events in Earth’s past are recorded by rock bodies such as the Flathead Sandstone and Chugwater Formation, etc. The images below show periods when campus was near the shoreline.
Surface/Sea Level Change. Has the area where BYU-Idaho resides ever been covered by relatively deep ocean?
Answer
Yes, many, many times! These events in Earth’s past are recorded by rock bodies such as the Madison, Gallatin, and Big Horn Formations. The image below shows an equatorial shallow sea covering the BYUI area.
Tectonic Change. Has the area where BYU-Idaho resides ever not existed? That is, was there ever a time when North America had not yet been formed?
Answer
Yes! When Earth formed, it was covered by craters and had no continents. The oldest continental rock formed about 140 million years after Earth formed (at about 4.4 bya), the oldest know part of North America formed approximately 540 million years after Earth’s formation (at about 4 bya), and the core of North America formed approximately 2.5 billion years after Earth formed! These events in Earth’s past are recorded by the oldest rock bodies observed on our field trip. The slide below uses distances to illustrate ages associated with the formation of North America.
Impact Change. Has the area where BYU-Idaho resides ever been affected by meteorite impact?
Answer
Yes, many times—especially early in Earth’s history. Most recently, the BYU-Idaho area was affected by the end-Mesozoic impact event. When the asteroid hit the Yucatan Peninsula approximately 65.5 million years ago, BYU-Idaho resided near an interior seaway (ocean). The impact was recorded by rock bodies such as those deposited in that seaway. The slide below illustrates the impact and the post-impact character of the northern Yucutan.
Biologic Change. Has the area where BYU-Idaho resides ever been occupied exclusively by single-celled organisms? That is, has there ever been a time when there were no multicellular animals or plants on Earth?
Answer
Yes, there have not been any multicellular organisms on Earth during most of its history! These events in Earth’s past are recorded by rock bodies across the planet. The first multicellular organisms appear about 900 Mya. The earliest fossils on Earth are stromatolites. The slide below uses distances to illustrate ages associated with the development of life.
Biologic Change. Has the area where BYU-Idaho resides ever been occupied by dinosaurs?
Answer
Yes, for a short time (about 185 My) during the Mesozoic Era. The slide below uses distances to illustrate the period when dinosaurs existed on the planet. It also shows some images of dinosaurs, including of a fossil that preserved dinosaur feathers (lower right).
Biologic Change. Has the area where BYU-Idaho resides ever not been inhabited by humans?
Answer
Yes, humans have lived only a short time on Earth and not until approximately 14 kya in this area. The image below describes and illustrates the periods of human existence.
Earth’s Normal State
Watch this video (5.5 minutes) that shows how the normal state of Earth is in constant change. When you hear the word “Geosphere”, it is referring to all the areas that make up the earth.
So, just how much has Earth changed? More than you can likely imagine! What is normal for Earth is constant change, not a set of average conditions—and certainly not average modern conditions.
