Evidence of the Earth's History (HS-ESS1-6): Apply scientific reasoning and evidence from ancient Earth materials, meteorites, and other planetary surfaces to construct an account of Earth's formation and early history
To construct an account of Earth's formation and early history, scientists apply reasoning and gather evidence from various sources, including ancient Earth materials, meteorites, and the surfaces of other planets. By studying rocks, minerals, and fossils found in Earth's crust, as well as the composition and age of meteorites, scientists can infer the processes that led to the formation of the planet about 4.5 billion years ago. Additionally, comparing Earth’s features with those of other celestial bodies provides insights into the early conditions and events, such as the accretion of matter, planetary differentiation, and the impact of collisions, that shaped Earth's development. This evidence helps to piece together a timeline and a detailed understanding of Earth's origins and its early evolution.
Main Concepts:
Scientists estimate that the solar system formed about 4.6 billion years ago from a giant cloud of gas and dust called a solar nebula. As the nebula collapsed under its own gravity, it began to spin and flatten into a disk. The central region eventually became the Sun, and the remaining material in the disk began to form into planets, including Earth.
To understand Earth's formation and early history, scientists analyze ancient rocks and minerals from Earth's crust, as well as meteorites and other planetary surfaces. They use various techniques such as radiometric dating, isotopic analysis, and geologic mapping to piece together the timeline of events and the physical and chemical conditions that existed at each stage.
Radiometric dating is a method of determining the age of rocks and minerals using radioactive isotopes. By measuring the abundance of certain isotopes and their decay products, scientists can calculate the absolute age of a rock sample. This technique is used to determine the ages of ancient Earth materials and meteorites, providing valuable information about the timing and processes of Earth's formation.
The sizes and compositions of planets, moons, asteroids, and other solar system objects provide clues about the processes that formed them. For example, the large size of Jupiter and its composition of mostly hydrogen and helium suggest that it formed early in the solar system's history, when there was still a lot of gas and dust available to form planets. The rocky, metal-rich composition of Earth and other inner planets suggest that they formed through the process of accretion, where smaller bodies collided and merged to form larger bodies.
The impact cratering record on planetary surfaces provides evidence of the frequency and intensity of impacts throughout the solar system's history. By analyzing the distribution and characteristics of impact craters on Earth and other planets, scientists can infer the relative ages of different surfaces and the timing and effects of major impact events. This information can help to understand the history of the solar system, including the formation of the planets and the role of impacts in shaping their evolution.
NGSS Aligned Testing Question
One of the methods used to determine the absolute age of a rock is through the collection and analysis of zircon crystals. Zircon crystals have been found in some Appalachian Mountain regions. They grow in magma or semi-molten rock and are made of silicon, oxygen, and zirconium. Zircon crystals are ideal for age dating because they have the following characteristics:
Commonly formed in felsic igneous rocks
Found in numerous sediments, such as beach sand, river sediments, and wind (eolian) deposits
Have a very high melting temperature and hardness
High density but non-magnetic
Contain small but measurable amounts of uranium (which substitutes for the zirconium in the crystal lattice when the crystal grows)
Identify one characteristic of zircon crystals that makes them ideal for determining the absolute age of rocks found in the Appalachian Mountains. Explain how this characteristic can be used to determine absolute age.
Allow credit for containing/presence of uranium and a correct explanation. Acceptable explanations include, but are not limited to:
— Half of the uranium found in some of the zircon crystals will decay into a stable material after 4.5 billion years.
— Uranium is a radioactive substance that has a constant rate of decay, which allows it to be used for dating rock samples.
— Uranium is a radioactive substance that decays at a predictable rate, so the amount of uranium that remains can be used to determine the age of the rock.
— The exponential decay of uranium in the rock allows for the radiometric dating of the rocks in the Appalachian Mountains.
General Question and Answer Section
When did Earth form? Answer: Earth formed 4.6 billion years ago.
What types of evidence do scientists use to construct an account of Earth's formation and early history? Answer: Scientists use various types of evidence, such as ancient Earth materials, meteorites, and other planetary surfaces.
How do scientists determine the absolute ages of ancient materials? Answer: Scientists use radiometric dating to determine the absolute ages of ancient materials.
What do the sizes and compositions of solar system objects provide clues about? Answer: The sizes and compositions of solar system objects provide clues about how they formed.
How can the impact cratering record of planetary surfaces help scientists understand the history of the solar system? Answer: The impact cratering record of planetary surfaces can help scientists understand the history of the solar system by revealing the frequency and timing of major events, such as the formation of the Moon.
What can the study of meteorites tell us about the early solar system? Answer: The study of meteorites can tell us about the early solar system by revealing the composition and structure of the materials that formed the planets.
How does the age of oceanic crust increase with distance from mid-ocean ridges? Answer: The age of oceanic crust increases with distance from mid-ocean ridges as a result of plate spreading.
How does the North American continental crust differ from the surrounding continental crust? Answer: The North American continental crust contains a much older central ancient core compared to the surrounding continental crust as a result of complex and numerous plate interactions.
What is radiometric dating? Answer: Radiometric dating is a method of determining the age of an object by measuring the amount of a radioactive isotope it contains.
What is plate tectonics? Answer: Plate tectonics is the theory that Earth's outer shell is divided into several plates that move and interact with one another, causing earthquakes, volcanic activity, and the formation of mountains and ocean basins.
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Disclaimer: The information provided is intended to serve as a study guide based on a contextual analysis of the NGSS standards for the Earth and Space Science assessment. These study guides should be used as a supplement to your overall study strategy, and their alignment to the actual test format is not guaranteed. We recommend that you consult with your instructor for additional guidance on exam preparation.