Bretz’s Boulderstrewn Home Now For Sale
Hi gang, We wouldn’t normally help advertise a home sale, but J Harlan Bretz’s home “Boulderstrewn” in Illinois just went on sale. There’s great interest in getting a buyer who has an interest or connection to the history of the home. Find more info here.
Moses Coulee: An Ice Age Enigma
Washington state is famous for its dramatic landscapes, many carved by the immense power of the Ice Age Floods. We know the stories of the Grand Coulee, Palouse Canyon, and the Potholes. But tucked away in north-central Washington, cutting a path from northeast to southwest across the Okanagan Plateau, lies Moses Coulee – perhaps the most mysterious of them all. Unlike its famous cousins, Moses Coulee doesn’t quite fit the standard narrative. Its head seemingly emerges from beneath the Wisconsin Withrow Moraine, and its very formation presents a fascinating puzzle for geologists. Flood Theories and Questions: An Enigma The Grand Coulees (Upper and Lower) are widely believed to have been carved by the spectacular Missoula Floods. These colossal deluges were unleashed when the Okanagan Lobe of the Cordilleran Ice Sheet blocked the Columbia River, redirecting massive amounts of water southward. For Moses Coulee, it’s not so clear-cut. While cataract retreat due to massive floodwaters is generally assumed, most theories suggest the Okanagan Lobe effectively blocked the Missoula Floods from entering Moses Coulee. So, what carved this impressive landscape? Enter J. Harlan Bretz, the pioneering geologist who first championed the idea of colossal floods shaping the Pacific Northwest. Bretz observed a distinct wide bench within Moses Coulee, high above its floor. This led him to speculate about two distinct periods of glacial floods: An older, pre-Wisconsin “Spokane Flood” that initially carved Moses Coulee. A later Wisconsin period flood (what we now call the Missoula Floods) that deepened the coulee floor. Interestingly, current speculation suggests the Upper Grand Coulee might also owe its primary formation to these earlier “Spokane Floods,” with the Lower Grand Coulee being a product of the later Missoula Floods. It seems the story of Washington’s coulees is far more layered than once thought! Beyond Glacial Lakes: A Subglacial Hypothesis But wait, there’s another fascinating idea. Some investigators propose that Moses Coulee wasn’t carved by the well-known Missoula or Columbia glacial lake outbursts at all. Instead, they suggest outbreak floods from under the ice sheet itself. Joel Gombiner and Jerome Lesemann have explored this idea, suggesting that the immense pressure of the overlying ice lobe could have forced subglacial meltwater to flow uphill over topographic highs. This water would then have exited from under the ice, becoming the powerful floodwaters that sculpted Moses Coulee. Imagine that — floods erupting from beneath a massive glacier! Explore the Mystery Yourself The interplay between the Withrow Moraine and the unique features of Moses Coulee makes this a truly captivating area for exploration, especially for those intrigued by the raw power of ancient ice and water. To truly enhance your visit to this less-traveled gem, we highly recommend: Watching several of Nick Zentner’s insightful videos where he dives deep into these Moses Coulee questions. His engaging explanations bring the geology to life! Examining J. Harlan Bretz’s original field notes, meticulously organized in geolocated Google Maps by Glenn Cruickshank. It’s like stepping back in time with the pioneering geologist himself. Moses Coulee is more than just a landscape; it’s an ongoing geological debate etched into the earth. Are you ready to explore this remarkable natural mystery? AI-assisted article by Lloyd DeKay – Columbia River Gorge Chapter
Ice Age FloodFest 2025 – Sat. July 26th
Get ready for the Ice Age Floodfest 2025 on July 26th, an unparalleled celebration of the cataclysmic events that carved out the Pacific Northwest’s iconic channeled scablands! Dive deep into the geological story that spans millennia and reshaped the very landscape beneath our feet. From towering coulees to vast dry falls, the evidence of these ancient, colossal floods is everywhere, and this year’s Floodfest promises to raise your awareness and understanding of their incredible power and lasting impact. Join us in the Lower Grand Coulee for a day of expert-led talks, fascinating field trips, and engaging exhibits that will transport you back to a time when mile-high ice dams burst, unleashing torrents of water that dwarfed any flood in human history. Whether you’re a seasoned geologist or simply curious about the natural wonders around you, the Ice Age Floodfest 2025 is an event you won’t want to miss! Presenters will share their knowledge and their appreciation of Ice Age Floods Geology, the Channeled Scablands, Shrub Steppe Ecosystems, Anthropology, Archeology, and History. Field Trip Hike: 9:00 AM – 10:30 AM Where: Lake Lenore Caves Heritage Area Bruce Bjornstad, a Research Scientist based in Richland, Washington and author of the popular ‘On the Trail of the Ice Age Floods’ guidebooks, will lead an educational hike from the Lake Lenore Caves trailhead. The park is situated above Lake Lenore, and it offers stunning views of the valley. The caves themselves are shallow basalt formations created during the Great Missoula floods. Outdoor Booths: 10 AM – 3 PM on the campus of Dry Falls Visitor Center. Featuring Federal, State, Confederated Tribes of the Colville Reservation, Nonprofits, Historians, Authors, & Volunteers Where: Dry Falls Visitor Center – Sun Lakes Dry Falls State Park 35661 HWY 17 North, Coulee City, WA 99115 Ice Age Floods Institute – Lower Grand Coulee Chapter and other Ice Age Flood Institute chapters from Oregon, Idaho, Montana, and Washington. The Confederated Tribes of the Colville Reservation will have historic photographs telling the story and the history of the Confederated Tribes of the Colville Reservation. They will also share the legends of the beautiful landscape of the Dry Falls area and surrounding landscape. Dr. Karen Capuder – Anthropologist and Senior Archaeologist Colville Tribes, will share some of the cultural and political history of the Colville Tribes, from time immemorial to the present day. Grant County Historians/authors: Dan Bolyard & John M. Kemble – Dan Bolyard has been a lifelong Grant County Big Bend area resident and railroad historian. John M. Kemble is a local historian and explorer highlighting Dry Falls, Sun Lakes, Steamboat Rock, The Grand Coulee, and Banks Lake. North Central Regional Library –April Harward, learn about the NCW Summer Library programs – captivating storytelling to engaging workshops and fun activities, everyone can unleash their unique voice and explore their passions. National Park Service – Justin Radford, Program Manager for the Ice Age Floods National Geologic Trail with a Mobile Interpretive Center showcasing the Ice Age Floods National Geologic Trail, the Lake Roosevelt National Recreation Area, and The Grand Coulee a National Natural Landmark. Foster Creek & Columbia Basin Conservation Districts – programs on Shrub Steppe ecology, water resources, wildlife, and native vegetation. Washington Department of Wildlife – wildlife found in Eastern Washington as well as the enhancement and preservation work that is done in the Columbia Basin. Archeologist – Mark Amara, Kim Lancaster, and Kellie Green; representing the Cascadia Conservation District, USDA Natural Resources Conservation Service. Their booth will highlight the importance of historical artifacts, tools of the trade, and hands-on activity too. Bureau of Reclamation – will have an overview of the Columbia Basin Irrigation Project, and the Grand Coulee Dam. Presentations: 10 am – 3 pm Where: inside/upstairs in the Dry Falls Visitor Center 10 am – 11 am: Justin Radford, Program Manager, NPS, Ice Age Floods National Geologic Trail, will present an overview of this unique geologic trail starting in Montana, through Idaho, Oregon, and Washington. Interpretive Specialist, David McWalter, will present an overview of Washington’s Ice Age Floods, introduce the rugged terrain of eastern Washington that was shaped by floods of unimaginable power during the last ice age, and share how the scientific views of the landscape have changed over the last century. 11:30 am – 12:30 pm: WA DNR, Geologists, Daniel Coe & Joel Gombiner, will present an update on recent studies of Washington’s Ice Age Floods and introduce a new lidar-based visualization of Dry Falls. 1 pm – 2 pm: WA State Parks, Interpretive Specialist 1, Sarah Overby will present “Brushstrokes: The Colorful Story of Lichen“. From rocks, trees, soil, and pretty much anything that will sit still long enough, lichen will spring up in robust colonies. Crusty, leafy, or even… fuzzy? They paint beautiful bright oranges and greens across the dark basalt rock and the branches of the sagebrush, but what are they doing there? This 45-minute presentation aims to dive deeper into the complexities of lichen and discuss its impact on ecosystems as well as its impact on us. 2:30 pm – 3:00 pm: Viewing of Bruce Bjornstad’s – “Ice Age Floodscapes” Bretz’ Great Cataract Group Primordial Potholes Coulee Grand Coulee – NW Exposures Dry Falls Deep Lake Potholes Dry Falls Visitor Center – weather station – up-to-date weather conditions at Dry Falls provided by the National Park Service. Watch a timelapse of the past 24 hours by clicking on the small photo, enlarge, press play, and enjoy!
IAFI Gorge-ous Gathering 2025 Explored the Columbia River Gorge
The 2025 Gorge-ous Gathering, the annual membership meeting of the Ice Age Floods Institute (IAFI), was an unqualified success! Hosted by the Columbia River Gorge Chapter, this year’s event treated nearly 150 participants to an unforgettable experience filled with geological exploration, natural beauty, and engaging presentations. Attendees enjoyed a diverse and packed program of discovery that included: Five immersive field trips: These excursions offered unique perspectives on the region’s geology, ecology, and cultural heritage. A lively membership meeting and dinner: A chance for members to connect, reflect, and look ahead. A captivating presentation by Nick Zentner: The renowned geologist enthralled the audience with his insights into J. Harlen Bretz’s groundbreaking Ice Age Floods theories. A post-field trip social gathering: An opportunity for attendees to unwind at Bargeway, a local pub, and discuss the day’s adventures. Exploring Wonders of the Gorge: Many first-time visitors were awed by the Columbia River Gorge, and by the Discovery Center which served as the main venue. The event also highlighted other local gems, including museums, wineries, and natural attractions. For the adventurous, there was even a wild and scenic whitewater rafting experience! The Columbia Gorge weather was characteristically warm and windy, except for the breezy and cool main field trip, and spirits were high throughout the event. The field trips were a definite highlight: Ice Age Floods of the Eastern Gorge: USGS geologists Jim O’Connor and Richard Waitt led a fascinating tour exploring the geology and iconic Ice Age Floods features of the eastern Gorge. Vineyards and Terroir: Renowned soil scientist Alan Busacca guided a tour of several local vineyards and wineries, illustrating how the unique “terroir”—including soil profile, precipitation, elevation, and exposure—contributes to an amazing spectrum of fine Gorge wines. Native Plant Walks: Native plant expert Barbara Robinson, who has dedicated years to reintroducing native plant landscapes at the Discovery Center, led insightful walks across the Rowena plateau and around the center’s grounds. Central Gorge Exploration: Local geologist Lloyd DeKay led a couple of trips, uncovering unusual geological features, sharing Native American cultural artifacts and stories, and even including a side trip to see a variety of exotic animals found in the central Gorge. Engaging Presentations and Community Spirit: Beyond the field trips, the Gorge-ous Gathering offered engaging presentations that fostered a strong sense of community, including: Nick Zentner’s Revelations: Always entertaining and dynamic, Nick Zentner captivated a near-capacity audience with his revelations about the observations, thoughts, and research that underpinned J. Harlen Bretz’s revolutionary theories on the Ice Age Floods. Welcomes: Krystyna Wolniakowski, Executive Director of the Columbia River Gorge National Scenic Area, welcomed IAFI members with a brief overview of the Scenic Area’s importance. IAFI President Gary Ford then provided a concise recap of the Institute’s beginnings and history, followed by the re-election of officers. The IAFI Store, expertly managed by Patty Hurd, saw brisk business. Numerous volunteers generously offered their help with check-ins, bus monitoring, and countless other details that ensured the smooth operation of this multi-faceted event. Venue: The invaluable support and resources provided by the Discovery Center perfectly complemented the theme of the entire gathering. Looking Ahead to 2026 Prepare to Mark Your Calendars! The 2026 annual membership meeting will be hosted by the Ellensburg Chapter. They are already hard at work planning and arranging exciting field trips, presentations, and social gatherings to delight members and the general public. Keep an eye on the IAFI.org website for more information, especially after the first of the year, to ensure you don’t miss out on the next incredible IAFI gathering!
Palouse Falls State Park
Palouse Falls State Park, dedicated in 1951, is a 94-acre park showcasing the dramatic Palouse Falls and its unique geological history. The park is a popular destination for viewing the falls, which were formed by Ice Age floods and are a key part of the Ice Age Floods National Geological Trail. The falls were designated as Washington’s state official waterfall in 2014, thanks to the advocacy of schoolchildren from Washtucna. Palouse Falls is one of four of the last remaining year-round waterfalls on the Palouse River that once stood in the path of the ice age floods. It is rich in both geological and human history. The native Palouse Indians called it “Aput Aput” meaning “falling water.” They believed that it was created by the Great Spirit because of his displeasure with the wicked Indians who lived further upstream. This obstacle was a barrier that allowed the salmon to travel no further. Sam Fisher, a Palouse Indian, also tells the story of how four giant brothers and their giant sister used oil from beaver tails to keep their hair shiny. Needing more oil, they searched for the giant beaver and fought with him. All four falls on the river were made when the beaver slapped his tail. At the last battle at Palouse Falls, the beaver struck his tail one last time creating the falls and the bowl it falls into. The vertical cracks in the basalt were made by the claws of the beaver. Palouse Falls has made a powerful impression on all who have visited. For example, one of the fall’s earliest visitors, Laurence L. Dodd in 1867, described the site he saw this way: “just before descending the Snake River hill your eye rests on the grateful green bottom of the Palouse with its clear and pure waters, flowing into the turbid Snake and after ascending the Snake River hill to the northward and eastward, the eye sweeps over a vast extent of country rarely surpassed in rugged desolation and wildness.…” Dodd was accompanied by a few local citizens from Starbuck on horseback to witness the scene he described. Early access to the falls was either by train (many passenger trains would stop here for their passengers to look at the falls) or by coming in from the east side. Robert E. Strahorn, who built the railroad up the Palouse Canyon had the original idea of making Palouse Falls a State Park. But it was not until years later that Washtucna area resident and president of the Washtucna Community Service Club John H. Baumann really pushed the idea. In 1945, Palouse Falls State Park was created. It was dedicated on June 3rd, 1951. The 299 acres that make up the entirety of this vast park were donated by The Baker-Boyer National Bank of Walla Walla, J.M. McGregor of the McGregor Land and Livestock Company of Hooper, and Mrs. Agnes Sells, a resident of Washtucna. Palouse Falls State Park is located off Highway 261, which branches off Highway 260 out of Washtucna. The most popular season for visiting is in the spring when the river is at its highest from winter snow melt. However, each season has its own story to tell as these pictures show. Article by Lloyd Stoess, President IAFI Palouse Falls Chapter
Hells Canyon Caves Reveal When it was Cut
The origin story of Hells Canyon, North America’s deepest river gorge, has long been unclear to scientists. But new research estimates it formed about 2.1 million years ago when a dramatic flood event likely created a river over the deep gorge. The researchers made the finding after studying clues hidden in the landscape and river deposits preserved in caves. They described their findings in a study published May 19 in the journal PNAS>. Hells Canyon borders Oregon, Idaho and Washington. It’s cut through by the Snake River and is North America’s deepest river gorge, at 10 miles (16 kilometers) wide and about 1.5 miles (2.4 km) deep — almost 2,000 feet deeper than the Grand Canyon. Canyons are inherently difficult to understand and date, said study lead author Matthew Morriss, a geologist at the Utah Geological Survey. “As a river erodes and carves a canyon, it sort of destroys the evidence of its own history,” Morriss told Live Science. But because Hells Canyon is so steep, he guessed it was carved quickly. To find out how the gorge formed, the team examined caves along the side of the canyon. When floods cause rivers to swell, they can deposit sediment into caves where it’s then preserved, Morriss said. The researchers analyzed gravel deposited by the Snake River in three caves along the sides of Hells Canyon, and estimated the age of the deposited material using isotope dating. This enabled the researchers to determine when the river was higher than its current level, which would have been when it was shaping the canyon. The team combined this information with the locations of knickpoints — drastic changes in river steepness where the rivers connect to the gorge — to piece together Hells Canyon’s history. These clues suggest that Hells Canyon formed when water diverted from Lake Idaho into the current route of the gorge to form what’s now the Snake River. The lake may have spilled over because of higher precipitation, or changes to the continental divide, Morriss said. This caused a river to form a path over the area that’s now Hells Canyon, and the water slowly began eroding rock about 5 million years ago, then carved the gorge much more quickly from about 2.1 million years ago. The canyon’s age was unexpected. “The age of the canyon was so much younger than I thought it would be,” Morriss said. “I had no idea it could be as young as 2 million years old — that’s younger than the Grand Canyon, which most people think could be about 5 million years old.” Hells Canyon has a lot in common with the Grand Canyon, according to Karl Karlstrom, geologist at the University of New Mexico whose work focuses on the Grand Canyon, and who was not involved with the new research. “The Grand Canyon and Hells Canyon always get compared to each other,” said Karlstrom. “They’re both big canyons with big rivers at the bottom, they’re about the same length and the same width,” Karlstrom told Live Science, but this study gives a clear picture of Hells Canyon’s distinct history. “To me this paper is a good hypothesis, and it paves the way for next generations of work,” Karlstrom said. Dating more caves in the canyon, and integrating other dating methodologies, could refine the findings and make the dates more precise, Karlstrom added. The findings can inform research on other canyons that may have been carved quickly by rivers, Morriss said. Understanding the history of Hells Canyon also gives insight into how the canyon’s formation shaped the surrounding ecosystem, as some animal species are divided by the canyon and others connected across it. Many landscape features of the southwestern U.S., like Hells Canyon and the Grand Canyon, are younger than previously expected. “[The] Western U.S. has a young and ever changing landscape that has been reshaped in the past few million years and is currently still adjusting,” Karlstrom said. This shows just how quickly — on the scale of geological time — a landscape can dramatically change, he noted. LiveScience article by Olivia Ferrari
Anthropoclastite – Rock Formed in 35 Years or Less
New research reveals industrial waste can turn into rock in as little as 35 years, instead of the thousands or millions of years previously assumed. The finding challenges what scientists know about rock formation, revealing an entirely new “anthropoclastic rock cycle.” The scientists found that waste from seaside industrial plants turns into rock especially rapidly due to the ocean water and air, which activate minerals such as calcium and magnesium in the waste, or slag, cementing it together faster than natural sediments. For a couple of hundred years, we’ve understood the rock cycle as a natural process that takes thousands to millions of years but these human-made materials are being incorporated into natural systems and becoming lithified — essentially turning into rock — over the course of decades instead. Researchers dubbed this newly discovered process the “rapid anthropoclastic rock cycle.” The findings challenge long-standing theories about how rocks form and suggest industries have far less time to dispose of their waste properly than previously thought, Owen said in the statement. The research was published April 10 in the journal Geology. Researchers discovered the first clues of turbo slag-to-rock transformation on Derwent Howe, a giant pile of waste from now-closed iron and steelmaking plants on the northwest coast of England. The scientists noticed irregular formations in these slag “cliffs,” prompting them to take a closer look. One sample contained an aluminum can tab, with a design that couldn’t have been manufactured before 1989, embedded in the material that helped the researchers estimate how long it takes for slag to lithify. For the can tab to become encased in rock, the slag must have solidified and lithified in the past 35 years. It’s possible that these processes finished earlier, so 35 years is the maximum time it takes to turn slag into rock. Scientists have previously made similar observations on the coast of Spain in the Gorrondatxe area, the researchers noted in the study, but those observations didn’t come with a time frame. Excerpted from a LiveScience article by Sascha Pare
The Earth – A Brief Overview
Background The 4.5 billion-year-old Earth is the only known astronomical object to harbor life, giving rise to billions of species of stunning diversity, including ours, Homo sapiens. It has formed the backdrop of an estimated 110 billion human lives. At 13.1 septillion pounds and 25,000 miles in circumference, the third planet from the sun long formed the horizon of all human experience and knowledge (watch overview). Recent discoveries have revealed our home planet’s relative size and location in the universe: a pale blue dot within the Orion Spur, located 26,000 light-years from the center of the Milky Way Galaxy, one of 100,000 galaxies within the Laniakea Supercluster. Formation Early Earth is theorized to have formed alongside the other planets within a solar nebula, where a massive cloud of spinning, interstellar gas and dust contracted under its own gravity and flattened into a hot disk (watch visualization). The core of the disk became dense with lighter elements like hydrogen, eventually heating up and triggering nuclear fusion, forming the sun. Solar wind pushed lighter elements farther out into the system, while heavier metals like iron gathered into increasingly larger masses known as planetismals in a process called accretion to form the Earth and other inner rocky planets. As the protoplanet grew, heat from the colliding material and radioactive decay differentiated Earth’s heavier iron-rich core from its lighter rocky mantle, giving rise to Earth’s magnetic field and long-term stability. Various models suggest Earth’s formation took tens of millions of years. Two billion years later, Earth changed dramatically when cyanobacteria, a microbe, evolved to generate energy from sunlight (i.e., photosynthesis) and release oxygen as a byproduct into the atmosphere during the Great Oxidation Event. Structure and Composition Earth is the densest planet in the solar system and the most massive of the four rocky terrestrials. Shaped into a sphere by gravity, Earth is flattened at its poles and bulges at its equator due to its roughly 1,000-mile-per-hour eastward spin (Jupiter spins 28 times faster). By analyzing seismic waves, researchers theorize that a solid, 9,800-degree Fahrenheit inner core is surrounded by an outer core of liquid iron and nickel—common elements that consolidate into solids at high pressures. Above the core, a slow-moving rocky mantle moves the crust’s tectonic plates, causing volcanoes and earthquakes (see overview). Earth’s spin combines with the core’s electrical conductivity and extreme heat to produce a magnetic field that protects its surface from damaging solar winds, cosmic rays, and deep space radiation. This so-called geodynamo process is expected to last for billions of years. Surface and Climate Situated within the solar system’s “Goldilocks zone,” Earth is the only planet with conditions able to sustain liquid surface water, key to the formation of life. Roughly 71% of its surface is water; the rest is land. An estimated 300 million planets in our galaxy are located in similar zones. The Earth’s five-layer atmosphere traps solar energy and maintains an average global surface temperature of 59 degrees Fahrenheit. Roughly 21% is oxygen, crucial for respiration but highly flammable. Nitrogen (78%) dilutes the oxygen and prevents rapid combustion. Seasons result from the Earth’s 23.4-degree tilt in relation to the orbital plane. Ice ages last millions of years and result from shifting climatic conditions—like ocean currents and the position of tectonic plates—that drop average temperatures by double digits. We live amid the fifth major ice age, though we are in the middle of a warmer interglacial period that began 11,000 years ago.
Yellowstone Supervolcano’s “Breathing” Cap Offers Eruption Insights
Scientists have discovered a “breathing” magma cap beneath the Yellowstone supervolcano, offering new clues about its eruption potential. This layer, located about 2.6 miles below the surface, acts like a lid on the magma reservoir. While this cap traps significant heat and pressure, it’s not completely sealed. Researchers found it to be porous, allowing for a gradual release of pressure. This natural venting mechanism may explain why Yellowstone hasn’t experienced a major eruption in hundreds of thousands of years. Using seismic waves the team mapped the upper boundary of the magma system. Their analysis indicates the cap consists of molten minerals and supercritical water bubbles within porous rock. Instead of building up to a critical point, the bubbles appear to be escaping through the cap’s pores, preventing a dangerous pressure surge. Professor Brandon Schmandt of Rice University compares this to “steady breathing,” noting that the volatile content is below levels typically preceding an eruption. The efficient venting of gas through cracks in the cap aligns with Yellowstone’s numerous hydrothermal features that release magmatic gases. This discovery provides a clearer picture of Yellowstone’s magma system and suggests that the risk of an imminent massive eruption might be lower than previously considered. The “breathing” cap offers a valuable insight into the volcano’s dynamics and highlights the ongoing processes that shape this remarkable geological wonder.
Our Pale Blue Dot
Background The 4.5 billion-year-old Earth is the only known astronomical object to harbor life, giving rise to billions of species of stunning diversity, including ours, Homo sapiens. It has formed the backdrop of an estimated 110 billion human lives. At 13.1 septillion pounds and 25,000 miles in circumference, the third planet from the sun long formed the horizon of all human experience and knowledge (watch overview). Recent discoveries have revealed our home planet’s relative size and location in the universe: a pale blue dot within the Orion Spur, located 26,000 light-years from the center of the Milky Way Galaxy, one of 100,000 galaxies within the Laniakea Supercluster. Formation Early Earth is theorized to have formed alongside the other planets within a solar nebula, where a massive cloud of spinning, interstellar gas and dust contracted under its own gravity and flattened into a hot disk (watch visualization). The core of the disk became dense with lighter elements like hydrogen, eventually heating up and triggering nuclear fusion, forming the sun. Solar wind pushed lighter elements farther out into the system, while heavier metals like iron gathered into increasingly larger masses known as planetesimals in a process called accretion to form the Earth and other inner rocky planets. As the protoplanet grew, heat from the colliding material and radioactive decay differentiated Earth’s heavier iron-rich core from its lighter rocky mantle, giving rise to Earth’s magnetic field and long-term stability. Various models suggest Earth’s formation took tens of millions of years. Two billion years later, Earth changed dramatically when cyanobacteria, a microbe, evolved to generate energy from sunlight (i.e., photosynthesis) and release oxygen as a byproduct into the atmosphere during the Great Oxidation Event. Structure and Composition Earth is the densest planet in the solar system and the most massive of the four rocky terrestrials. Shaped into a sphere by gravity, Earth is flattened at its poles and bulges at its equator due to its roughly 1,000-mile-per-hour eastward spin (Jupiter spins 28 times faster). By analyzing seismic waves, researchers theorize that a solid, 9,800-degree Fahrenheit inner core is surrounded by an outer core of liquid iron and nickel—common elements that consolidate into solids at high pressures. Above the core, a slow-moving rocky mantle moves the crust’s tectonic plates, causing volcanoes and earthquakes (see overview). Earth’s spin combines with the core’s electrical conductivity and extreme heat to produce a magnetic field that protects its surface from damaging solar winds, cosmic rays, and deep space radiation. This so-called geodynamo process is expected to last for billions of years. Surface and Climate Situated within the solar system’s “Goldilocks zone,” Earth is the only planet with conditions able to sustain liquid surface water, key to the formation of life. Roughly 71% of its surface is water; the rest is land. An estimated 300 million planets in our galaxy are located in similar zones. The Earth’s five-layer atmosphere traps solar energy and maintains an average global surface temperature of 59 degrees Fahrenheit. Roughly 21% is oxygen, crucial for respiration but highly flammable. Nitrogen (78%) dilutes the oxygen and prevents rapid combustion. Seasons result from the Earth’s 23.4-degree tilt in relation to the orbital plane. Ice ages last millions of years and result from shifting climatic conditions—like ocean currents and the position of tectonic plates—that drop average temperatures by double digits. We live amid the fifth major ice age, though we are in the middle of a warmer interglacial period that began 11,000 years ago. Reprinted from 1440 Daily Digest