https://www.khanacademy.org/science/middle-school-earth-and-space-science/x87d03b443efbea0a:the-geosphere/x87d03b443efbea0a:fossils-and-rock-layers/v/fossils-and-rock-layers 2023-08-04T17:42:39.696972153Z Fossils and rock layers Geologists use a geologic timescale to map Earth's 4.6-billion-year history. They study sedimentary rock layers, or strata, and fossils to understand past events. They use the Law of Superposition and the Law of Crosscutting Relationships to determine the relative ages of rock layers. This process, called relative dating, helps them trace the evolution of life on Earth. Khan Academy video https://cdn.kastatic.org/ka_thumbnails_cache/7974ab0f-0fcb-4caf-b76b-e0cf618645a5_1280_720_base.png Fossils and rock layers Geologists use a geologic timescale to map Earth's 4.6-billion-year history. They study sedimentary rock layers, or strata, and fossils to understand past events. They use the Law of Superposition and the Law of Crosscutting Relationships to determine the relative ages of rock layers. This process, called relative dating, helps them trace the evolution of life on Earth. https://cdn.kastatic.org/ka-youtube-converted/3LObb5WxMdw.mp4/3LObb5WxMdw.mp4 275 Inside the Earth https://www.khanacademy.org/science/middle-school-earth-and-space-science/x87d03b443efbea0a:the-geosphere/x87d03b443efbea0a:fossils-and-rock-layers/a/fossils-and-rock-layers 2022-05-11T01:10:19.383638514Z Fossils and rock layers Review your understanding of fossils and rock layers with this free article aligned to NGSS standards. article https://www.khanacademy.org/science/middle-school-earth-and-space-science/x87d03b443efbea0a:the-geosphere/x87d03b443efbea0a:fossils-and-rock-layers/e/apply-fossils-and-rock-layers 2022-04-29T22:55:37.196779892Z Apply: fossils and rock layers Apply your understanding of fossils and rock layers in this set of free practice questions aligned to NGSS standards. Lauren Rosebrugh exercise https://www.khanacademy.org/science/cosmology-and-astronomy/earth-history-topic/seismic-waves-tutorial/v/seismic-waves 2021-04-29T19:30:41Z Seismic waves S-waves and P-waves Sal Khan video https://cdn.kastatic.org/googleusercontent/3ejbQao8edErsPWzk4TplP5t2aUBahnxfkynq34LfhZo79k18RIRRbKUdCGW15YsMk9WQY9WVJLPa47olaG3u1ak Seismic waves S-waves and P-waves https://cdn.kastatic.org/ka-youtube-converted/NhioAAdYDJM.mp4/NhioAAdYDJM.mp4 518 Inside the Earth https://www.khanacademy.org/science/cosmology-and-astronomy/earth-history-topic/seismic-waves-tutorial/v/refraction-of-seismic-waves 2021-05-28T22:26:27Z Refraction of seismic waves Refraction of Seismic Waves Sal Khan video https://cdn.kastatic.org/googleusercontent/mRgmuW2G4w9EMGenE2nVonJqdkTr0NlZAo6iRty5wZA1jQu_O80AjCSyPFSSgBWEnxQhSxvhDyU300iqFxydJae5 Refraction of seismic waves Refraction of Seismic Waves https://cdn.kastatic.org/ka-youtube-converted/UNZ171fDja4.mp4/UNZ171fDja4.mp4 562 Inside the Earth https://www.khanacademy.org/science/cosmology-and-astronomy/earth-history-topic/seismic-waves-tutorial/v/why-s-waves-only-travel-in-solids 2021-04-26T14:33:09Z Why S-waves only travel in solids Why S-Waves Only Travel in Solids Sal Khan video https://cdn.kastatic.org/googleusercontent/47adyeiJPZEcqLLEvNOd6ljO4SBnVmaYntqfn13vIbkr6vitd6qxPsobiFhW_-xpc8xZVs-V_W3jRXfpfCuY1S3n Why S-waves only travel in solids Why S-Waves Only Travel in Solids https://cdn.kastatic.org/ka-youtube-converted/BTWLwoaNeBA.mp4/BTWLwoaNeBA.mp4 255 Inside the Earth https://www.khanacademy.org/science/strengthened-shs-earth-and-space-science-1/x006d5d274c051fd7:origin-and-structure-of-the-earth/x006d5d274c051fd7:inside-the-earth/v/yellowstone-monitoring-the-fire-below 2023-11-08T23:44:11.024924004Z Yellowstone—Monitoring the Fire Below Three of the most catastrophic volcanic eruptions in geologic history occurred at a place now visited by nearly four million people a year: Yellowstone National Park. The magma chamber responsible still lies beneath, and continues to steam, heat, and shift the park landscape. We talk with the geologists regularly monitoring these disquieting signals to understand where this active region lies in its volcanic lifespan. American Museum of Natural History video https://cdn.kastatic.org/googleusercontent/ZCdwTudJg6e6n-P2gsaUborP4izvMsGo71pvEVlX9dNYWcLXcP7VHkWpn2grt4TUP1KoJLQP9NswyHBuBLSFTBw Yellowstone—Monitoring the Fire Below Three of the most catastrophic volcanic eruptions in geologic history occurred at a place now visited by nearly four million people a year: Yellowstone National Park. The magma chamber responsible still lies beneath, and continues to steam, heat, and shift the park landscape. We talk with the geologists regularly monitoring these disquieting signals to understand where this active region lies in its volcanic lifespan. https://cdn.kastatic.org/ka-youtube-converted/rFe-VSf-TQ8.mp4/rFe-VSf-TQ8.mp4 435 Inside the Earth https://www.khanacademy.org/science/strengthened-shs-earth-and-space-science-1/x006d5d274c051fd7:origin-and-structure-of-the-earth/x006d5d274c051fd7:inside-the-earth/a/volcanoes-101 2025-03-07T16:48:43.939590077Z Volcanoes 101 article https://www.khanacademy.org/science/strengthened-shs-earth-and-space-science-1/x006d5d274c051fd7:origin-and-structure-of-the-earth/x006d5d274c051fd7:inside-the-earth/e/quiz-volcanoes 2026-04-07T23:55:07.30621384Z Quiz: Volcanoes AMNH exercise https://www.khanacademy.org/science/cosmology-and-astronomy/earth-history-topic/plate-techtonics/v/compositional-and-mechanical-layers-of-the-earth 2024-12-18T15:07:32.868904839Z Compositional and mechanical layers of the earth The crust is the outermost layer of Earth and is composed of solid rock. The lithosphere contains the crust and upper mantle. The mantle is the thickest layer and is made up of hot, mostly solid rock. The core is divided into two parts: the inner core and outer core. The inner core is solid and the outer core is liquid. Sal Khan video https://cdn.kastatic.org/googleusercontent/uVJeKygXh_meaGbmYVnz4o990MaLry8bphlGY-OCroNQqk1HwxlkqLpkHMiW37KT4E7yApsUnlwp72kuOgh68HQ Compositional and mechanical layers of the earth The crust is the outermost layer of Earth and is composed of solid rock. The lithosphere contains the crust and upper mantle. The mantle is the thickest layer and is made up of hot, mostly solid rock. The core is divided into two parts: the inner core and outer core. The inner core is solid and the outer core is liquid. https://cdn.kastatic.org/ka-youtube-converted/hHteUIS0OFY.mp4/hHteUIS0OFY.mp4 710 Inside the Earth https://www.khanacademy.org/science/cosmology-and-astronomy/earth-history-topic/plate-techtonics/v/how-we-know-about-the-earth-s-core 2021-04-26T14:33:09Z How we know about the earth's core S-wave shadow and P-wave detection patterns give us information about the core Sal Khan video https://cdn.kastatic.org/googleusercontent/XE-Igftx_eEslhuJt-sBdlUyPQ2LBP8nVVIHi8xPCyJa9mDz1-RVE8EzMdK0M433-cXL9ROCLNRW66A-GZpMJwRs How we know about the earth's core S-wave shadow and P-wave detection patterns give us information about the core https://cdn.kastatic.org/ka-youtube-converted/KL0i1RSnpfI.mp4/KL0i1RSnpfI.mp4 349 Inside the Earth https://www.khanacademy.org/science/cosmology-and-astronomy/earth-history-topic/plate-techtonics/v/structure-of-the-earth 2021-04-26T14:33:09Z Structure of the earth Structure of the Earth - crust, mantle, core Sal Khan video https://cdn.kastatic.org/googleusercontent/ozhNh79o7_IVg6IqpuKAMT4UDbW7Zxv4l7nou5mnROu6-3SOusY09cd0eOopptqM6utpcVPkbOpwPxC7Fk0ygwGGyw Structure of the earth Structure of the Earth - crust, mantle, core https://cdn.kastatic.org/ka-youtube-converted/4AxZ-6MOznY.mp4/4AxZ-6MOznY.mp4 573 Inside the Earth https://www.khanacademy.org/science/cosmology-and-astronomy/earth-history-topic/seismic-waves-tutorial/v/the-mohorovicic-seismic-discontinuity 2021-04-29T19:30:41Z The mohorovicic seismic discontinuity The Mohorovicic Seismic Discontinuity- boundary between crust and mantle (or Moho) Sal Khan video https://cdn.kastatic.org/googleusercontent/SlEFcUwz43LTs0M4VXT2ZjUVckT-S-ppOBsNfWk2DEgAje6EnqQX2IzCAFTz6G3vVpbeDq1kSe8nyZlU3oCPeycs The mohorovicic seismic discontinuity The Mohorovicic Seismic Discontinuity- boundary between crust and mantle (or Moho) https://cdn.kastatic.org/ka-youtube-converted/yAQSucmHrAk.mp4/yAQSucmHrAk.mp4 373 Inside the Earth https://www.khanacademy.org/science/middle-school-earth-and-space-science/x87d03b443efbea0a:the-geosphere/x87d03b443efbea0a:plate-tectonics/a/plate-tectonics-the-ocean-floor 2022-05-11T01:10:19.383638514Z Plate tectonics and the ocean floor Review your understanding of plate tectonics and the ocean floor in this free article aligned to NGSS standards. article https://www.khanacademy.org/science/strengthened-shs-earth-and-space-science-1/x006d5d274c051fd7:origin-and-structure-of-the-earth/x006d5d274c051fd7:inside-the-earth/a/plates-on-the-move 2025-03-07T16:50:49.734868403Z Plates on the Move article https://www.khanacademy.org/science/strengthened-shs-earth-and-space-science-1/x006d5d274c051fd7:origin-and-structure-of-the-earth/x006d5d274c051fd7:inside-the-earth/e/quiz-plate-tectonics 2026-04-02T16:36:17.676962277Z Quiz: Plate Tectonics American Museum of Natural History exercise