What is a key characteristic of the atmosphere on Uranus?

It has a tilted axis giving it extreme seasonal changes.

It experiences no weather changes.

Atmosphere of planets in our solar system

THE SOAR SYSTEM A solar system is a group of planets and other celestial bodies that revolve around a star. A solar nebula- a vast cloud of gas and dust, mostly hydrogen and helium. How the Solar System Form • COLLAPSE AND SPINNING DISK FORMATION - Gravity pulls material inward. The cloud flattens into a spinning disk due to conservation of angular momentum. • PROTOSTAR FORMATION- (BIRTH OF THE SUN). Material collects at the center, and begun to heat up. When it reaches to 10 million KELVIN, nuclear fusion begins. thus, SUN is born. • PLANETESIMALS AND PROTOPLANETS. Dust and gas in the disk stick together via static and gravitational forces. These form planetesimals, which grow into protoplanets collision and accretion. • PLANET FORMATION. Inner disk: too hot for gas rocky planets form Mercury, Venus, Earth, Mars. • PLANET FORMATION. Outer disk: gas and ice giants. Jupiter, Saturn, Uranus, Neptune • LEFTOVER DEBRIS. Remaining materials forms moon, asteroids, comets and dwarf planets. DIFFERENT HYPOTHESIS IN THE FORMATION OF SOLAR SYSTEM. 1. NEBULAR HYPOTHESIS- The Solar system formed from a rotating cloud of Gas and Dust (solar nebula). As it rotates conservation of angular momentum caused the cloud to flatten into a disk. the Sun formed at the center (DISK) while planets formed from the surrounding materials through acceleration. thus, it explains the coplanar and nearly circular orbit of the planets all planets orbits around the sun on the same flat, disk shaped plane. Proposed by Immanuel Kant in 1755 and Modified by Pierre Simon Laplace in 1756. PROTOPLANET HYPOTHESIS. The Solar system formed from a rotating cloud of Gas and Dust (solar nebula). As it rotates conservation of angular momentum caused the cloud to flatten into a disk. 2. Protoplanet hypothesis. Builds on the nebular model but focuses more on the role of planetesimals which then form into full planets. PROCESS: - Small solid particles stick together through collisions. As collisions takes place, it grows into kilometer-sized planetesimals. Gravitational interactions lead to the formation of planets. Lead to formation of steroids belts and varying planet sizes 3. Encounter hypothesis. States that the sun encountered a rogue star. The encounter led to the removal of hot gas from both stars due to their gravitational interaction. The hot gas then accumulated and formed the planets. The materials from the less dense rogue star formed the other planets, while that from the sun formed the inner planets. 4. TIDAL HYPOTHESIS. (also called the Tidal Theory) is an early scientific idea about how the solar system might have formed. Proposed by James Jeans and Harold Jeffreys. A massive star passed very close to the early Sun. The hot gas then accumulated and formed the planets. The materials from the less dense rogue star formed the other planets, while that from the sun formed the inner planets. Streams of hot gas were drawn out from the Sun in elongated shape. These streams eventually condensed and cooled, forming planets, moons, and other bodies in the solar system. 5. Not accepted theory. Later studies showed the streams of hot gas would disperse too quickly into space instead of condensing into planets. The theory also couldn’t explain the specific orbital patterns and compositions we see today. Modern science favors the Nebular Hypothesis, which explains solar system formation through the collapse of a rotating gas cloud. Earth as the only habitable planet 1. Right Distance from the Sun (The Goldilocks Zone). Not too hot, not too cold — just right for liquid water to exist. 2. Atmosphere with Oxygen. Earth has a mix of gases, especially oxygen, which most living things need to survive. 3. Liquid Water. Earth has oceans, rivers, and rain — water is essential for all life. 4. Magnetic Field. Earth’s magnetic field protects us from harmful solar radiation. 5. Stable Climate. The atmosphere and natural cycles keep temperatures and weather mostly stable over time. 6. Rich Resources. Earth has soil for growing food, minerals, and energy sources that support life and technology. Solar explorations 1. AUGUST 6, 2014. First space craft to orbit a comet (ROSETTA PROBE). Captures the comet photograph. -Comets have coma and tail as it approaches to the sun. 2. JULY 14, 2015. NASA’s New Horizons spacecraft made history by becoming the first spacecraft to fly by Pluto, giving us our first close-up look at the dwarf planet. First time visiting Pluto. Before this, Pluto was just a blurry dot in telescope images. Revealed a surprising world New Horizons showed mountains of ice, smooth plains, and a heart-shaped region called Tombaugh Regio. Changed what we knew. Scientists thought Pluto would be dull and frozen — instead, it turned out to be geologically active and incredibly complex. 3. SEPTEMBER 8, 2016. NASA launched OSIRIS-REx, the first U.S. mission to collect a sample from an asteroid and return it to Earth. Changed what we knew. Scientists thought Pluto would be dull and frozen — instead, it turned out to be geologically active and incredibly complex. OSIRIS-REx stands for: Origins, Spectral Interpretation, Resource Identification, Security–Regolith Explorer It was sent to study the asteroid Bennu, a near-Earth asteroid about 500 meters wide. Mission Goals: Collect a sample of surface material from Bennu Study the asteroid’s omposition, structure, and history. Mission Goals: Help scientists understand the origins of the solar system. Learn more about asteroids that could impact Earth. 4. August 12, 2018: Launch of NASA’s Parker Solar Probe, the first spacecraft to "touch" the Sun by flying through its outer atmosphere, called the corona. Mission Goal: To study the Sun up close and help scientists understand: How the solar wind (a stream of charged particles) is formed. Why the Sun’s corona is hotter than its surface. What causes solar storms that can affect Earth’s satellites and power grids. 5. November 26, 2018: NASA’s Insight Lander Touches Down on Mars. Its mission was focused on studying the interior of the Red Planet (crust, mantle, and core of the planet). Why the Sun’s corona is hotter than its surface. What causes solar storms that can affect Earth’s satellites and power grids 6. November 26, 2018: NASA’s Insight Lander Touches Down on Mars. Its mission was focused on studying the interior of the Red Planet (crust, mantle, and core of the planet) 7. JULY 30, 2020 PERSEVERANCE PROBE. Perseverance rover as part of the Mars 2020 mission aboard an Atlas V-541 rocket This marked a major step in Mars exploration. 8. DECEMBER 25, 2021-JAMES WEBB SPACE TELESCOPE. Investigate exoplanets’ atmospheres for signs of habitability. Observe the first galaxies formed after the Big Bang. Study the formation of stars and planetary systems. Look deeper into the infrared universe than ever before. RESULTS OF EXPLORATION • Evidence of Ancient Life-friendly Environment. • Sedimentary rocks formed in water-rich environments. • Signs of clay and carbonate minerals, which can preserve biosignatures (traces of past life). • Evidence of Ancient Life-friendly Environment. • Sedimentary rocks formed in water-rich environments. • Signs of clay and carbonate minerals, which can preserve biosignatures (traces of past life). • Evidence of Ancient Life-friendly Environment. • Sedimentary rocks formed in water-rich environments. • Signs of clay and carbonate minerals, which can preserve biosignatures (traces of past life).

Hello friends, welcome to a new Happy Learning video. Have you ever wondered how plants feed? To answer this question, we need to understand... photosynthesis. Photosynthesis is a process in which plants make their own food to be able to grow and develop. In order to perform photosynthesis, they need various elements: sunlight, carbon dioxide obtained from air, and water, and chlorophyll, which is a green substance that all plants have and is fundamental for performing photosynthesis since it could not happen without it. By the way, chlorophyll is what gives all plants their green color. But how does photosynthesis take place? Look at this plant. As you can see, its roots are anchored to the ground. And through them, the plant absorbs water and minerals in the soil. Water with minerals are transported up the stem, reaching the leaves. The leaves are full of tiny pores called stomata which absorb carbon dioxide that the air in the surrounding contains. All this containing water, minerals and carbon dioxide is called raw sap. Now it's chlorophyll's turn. The chlorophyll in the leaves has all the necessary ingredients for photosynthesis to take place. And when it receives sunlight, the process begins by transforming the raw sap into elaborated sap, which also circulates around the plant and works as food. All plants feed from elaborated sap, and they store it in their roots like a carrot, or in their fruit, like an apple or a pear. Now we know how photosynthesis takes place, but why is it so important? Without plants, there would be no life on Earth. We wouldn't have oxygen to breathe or food to feed on. You already know that herbivores eat plants, and carnivores eat herbivores. Plants are fundamental for the food chain. And they are also fundamental for our respiration. Actually, when humans breathe, we turn oxygen into carbon dioxide. Quite the opposite of when plants perform photosynthesis. A curious fact you need to know is that at night, because plants don't have sunlight to photosynthesize, they breathe like humans do. They take in oxygen and release carbon dioxide. Remember that. And one last thing so you understand the importance of photosynthesis. When plants absorb dirty and contaminated gases, they transform them into pure air, into oxygen, and this way they clean the atmosphere and all nature. Plants are the best solution to fight against contamination, don't you think? Goodbye friends and don't forget to subscribe to Happy Learning TV.

A solution is a mixture in which one or more substances are uniformly distributed in another substance. Solutions can be mixtures of liquids, solids, or gases. For example, plasma, the liquid part of blood, is a very complex solution. It is composed of many types of ions and large molecules, as well as gases, that are dissolved in water. A solute (SAHL-YOOT) is a substance dissolved in the solvent. The particles that compose a solute may be ions, atoms, or molecules. The solvent is the substance in which the solute is dissolved. For example, when sugar, a solute, and water, a solvent, are mixed, a solution of sugar water results. Though the sugar dissolves in the water, neither the sugar molecules nor the water molecules are altered chemically. If the water is boiled away, the sugar molecules remain and are unchanged. Solutions can be composed of various proportions of a given solute in a given solvent. Thus, solutions can vary in concentra- tion. The concentration of a solution is the amount of solute dis- solved in a fixed amount of the solution. For example, a 2 percent saltwater solution contains 2 g of salt dissolved in enough water to make 100 mL of solution. The more solute dissolved, the greater is the concentration of the solution. A saturated solution is one in which no more solute can dissolve. Aqueous (AY-kwee-uhs) solutions—solutions in which water is the solvent—are universally important to living things. Marine microorganisms spend their lives immersed in the sea, an aqueous solution. Most nutrients that plants need are in aqueous solutions in moist soil. Body cells exist in an aqueous solution of intercellu- lar fluid and are themselves filled with fluid; in fact, most chemical reactions that occur in the body occur in aqueous solutions. Copyright © by Holt, Rinehart and Winston. All rights reserved. Liquid water Solid water Ice (solid water) is less dense than liquid water because of the structure of ice crystals. The water molecules in ice are bonded to each other in a way that creates large amounts of open space between the molecules, relative to liquid water. FIGURE 2-12 solvent from the Latin solvere, meaning “to loosen” Word Roots and Origins CHEMISTRY OF LIFE 43 ACIDS AND BASES One of the most important aspects of a living system is the degree of its acidity or alkalinity. What do we mean when we use the terms acid and base? Ionization of Water As water molecules move about, they bump into one another. Some of these collisions are strong enough to result in a chemical change: one water molecule loses a proton (a hydrogen nucleus), and the other gains this proton. This reaction really occurs in two steps. First, one molecule of water pulls apart another water molecule, or dissociates, into two ions of opposite charge: H2O ∏ H OH The OH ion is known as the hydroxide ion. The free H ion can react with another water molecule, as shown in the equation below. H H2O ∏ H3O The H3O ion is known as the hydronium ion. Acidity or alkalin- ity is a measure of the relative amounts of hydronium ions and hydroxide ions dissolved in a solution. If the number of hydronium ions in a solution equals the number of hydroxide ions, the solution is said to be neutral. Pure water contains equal numbers of hydro- nium ions and hydroxide ions and is therefore a neutral solution. Acids If the number of hydronium ions in a solution is greater than the number of hydroxide ions, the solution is an acid. For example, when hydrogen chloride gas, HCl, is dissolved in water, its mol- ecules dissociate to form hydrogen ions, H, and chloride ions, Cl, as is shown in the equation below. HCl ∏ H Cl These free hydrogen ions combine with water molecules to form hydronium ions, H3O. This aqueous solution contains many more hydronium ions than it does hydroxide ions, making it an acidic solution. Acids tend to have a sour taste; how- ever, never taste a substance to test it for acidity. In concentrated forms, they are highly corrosive to some materials, as you can see in Figure 2-13. Bases If sodium hydroxide, NaOH, a solid, is dissolved in water, it dissociates to form sodium ions, Na, and hydroxide ions, OH, as shown in the equation below. NaOH ∏ Na OH Copyright © by Holt, Rinehart and Winston. All rights reserved. Eco Connection onnection Acid Precipitation Acid precipitation, more commonly called acid rain, describes rain, snow, sleet, or fog that contains high levels of sulfuric and nitric acids. These acids form when sulfur dioxide gas, SO2, and nitrogen oxide gas, NO, react with water in the atmosphere to produce sulfuric acid, H2SO4, and nitric acid, HNO3. Acid precipitation makes soil and bodies of water, such as lakes, more acidic than normal. These high acid levels can harm plant and animal life directly. A high level of acid in a lake may kill mollusks, fish, and amphibians. Even in a lake that does not have a very elevated level of acid, acid precipitation may leach aluminum and magnesium from soils, poisoning water- dwelling species. Reducing fossil-fuel consump- tion, such as occurs in gasoline engines and coal-burning power plants, should reduce high acid levels in precipitation. Sulfur dioxide, SO2, which is produced when fossil fuels are burned, reacts with water in the atmosphere to produce acid precipitation. Acid precipitation, or acid rain, can make lakes and rivers too acidic to support life and can even corrode stone, such as the face of this statue. FIGURE 2-13 44 CHAPTER 2 This solution then contains more hydroxide ions than hydronium ions and is therefore defined as a base. The adjective alkaline refers to bases. Bases have a bitter taste; however, never taste a substance to test for alkalinity. They tend to feel slippery because the OH ions react with the oil on our skin to form a soap. In fact, commercial soap is the product of a reaction between a base and a fat. pH Scientists have developed a scale for comparing the relative con- centrations of hydronium ions and hydroxide ions in a solution. This scale is called the pH scale, and it ranges from 0 to 14, as shown in Figure 2-14. A solution with a pH of 0 is very acidic, a solution with a pH of 7 is neutral, and a solution with a pH of 14 is very basic. A solution’s pH is measured on a logarithmic scale. That is, the change of one pH unit reflects a 10-fold change in the acidity or alkalinity. For example, urine has 10 times the H3O ions at a pH of 6 than water does at a pH of 7. Vinegar, has 1,000 times more H3O ions at a pH of 3 than urine at a pH of 6, and 10,000 times more H3O ions than water at a pH of 7. The pH of a solution can be measured with litmus paper or with some other chemical indicator that changes color at various pH levels. Buffers The control of pH is important for living systems. Enzymes can function only within a very narrow pH range. The control of pH in organisms is often accomplished with buffers. Buffers are chemi- cal substances that neutralize small amounts of either an acid or a base added to a solution. As Figure 2-14 shows, the composition of your internal environment—in terms of acidity and alkalinity— varies greatly. Some of your body fluids, such as stomach acid and urine, are acidic. Others, such as intestinal fluid and blood, are

Make examples like these: An experiment is conducted to determine the effects of classical music on the growth rate of marigolds. Two groups of plants grown from seeds in identical soil types, exposed to identical light conditions, and given the same nutrients. Group A is in a quiet atmosphere. The plants in Group B are provided with the same atmosphere, except that classical music is played for 12 hours daily in this area. The scientist measures the plant growth in both groups reach day and records the data. Find the independent variable and dependent variable, along with experimental groups and control group, with constants and variables not controlled.

Create a quiz with the following questions and answersConvection is… The rising motion of warm air A large volume of air A boundary between two different air masses The weight of the Earth’s atmosphere over an area What are isobars? Storms with strong winds, heavy rains, lightning, and thunder Lines on a map to show high and low pressure The study of elevation This front is associated with thunderstorms, heavy rain, snow, and cooler temperatures. Warm front Stationary front Cold front Occluded front What is a barometer? A tool used to measure temperature An instrument used to measure wind speed An instrument used to measure humidity An instrument used to measure air pressure What is a tornado? Storms with strong winds, heavy rains, lightning, and thunder Large, rotating tropical weather systems A rapidly spinning column of air that has touched the ground What is topography? The study of elevation Lines on a map to show high and low pressure The condition of the atmosphere at a given place and time What are air masses? Large, rotating tropical weather systems The study of elevation A large volume of air with the same temperature What is transpiration? The process of a liquid’s surface changing into a gas The process of a gas changing into a liquid The movement of water through the soil The process of water vapor being released by plants. What is nitrification? The process bacteria use to convert nitrogen gas into ammonium ions The process of turning ammonium ions into nitrites and nitrates. The uptake of nitrates in the soil by the roots of plants. The process of turning nitrates into nitrogen gas Fun Fact: Carbon makes up ___ of your mass. 30% 18% 50% 6% What are the reactants of photosynthesis? Carbon dioxide and water Glucose and oxygen What are the reactants of cellular respiration? Carbon dioxide and water Glucose and oxygen What is a storm surge? Flooding caused by hurricanes Region of air where the air pressure is low Any product of the condensation of water vapor High pressure is… A region of air where the air pressure is greater than that of the surrounding area A region of air where the air pressure is lower than that of the surrounding area. Low pressure is… A region of air where the air pressure is greater than that of the surrounding area A region of air where the air pressure is lower than that of the surrounding area. What causes global winds? Photosynthesis The process carbon goes through Uneven heating of the Earth What can humans do to reduce carbon emissions? We can use renewable energy (ex. solar power) We can use non-renewable energy (ex. fossil fuels) Carbon can form stable bonds with many elements and and makes up the backbone of major macromolecules: carbohydrates, proteins, lipids, and ___ Nucliec acids Glucose Oxygen Nitrogen What weather is associated with low-pressure systems? Bad weather (ex. Cloudy weather) Good weather (ex. Sunny weather) What is fossilization? The burning of fossil fuels The process where fungi and bacteria decompose dead organisms Dead organisms form fossil fuels over thousands and millions of years What is the first step in the formation of tornadoes? Rising air from the ground pushes up on the swirling air and tips it over A large thunderstorm occurs in a cumulonimbus cloud The funnel grows longer and stretches towards the ground The funnel of swirling air begins to suck up more warm air from the ground What is the difference between thunderstorms and regular storms? Thunderstorms have thunder while regular storms don’t Regular storms have thunder while thunderstorms don’t There is no difference What are hurricanes? Rapidly spinning columns of air touch the ground Large, rotating tropical weather systems Storms with strong winds, heavy rains, lightning, and thunderstorms What is not a hurricane fact? They are the most powerful storms on earth They have an average wind speed of 120-180 km/h They lose their power when they travel over cooler waters or land Storm surges cause the most damages What is the difference between weather and climate? Weather is long-term while climate is short-term Climate is long-term while weather is short-term There is no difference

Based on the provided sources, here is a comprehensive extraction of the information regarding the water cycle, energy transfer, and Earth's wind systems, organized into key points: The Water Cycle and Its Reservoirs • Definition: The water cycle is the continuous movement of water among various reservoirs on Earth. • Water Reservoirs: These are storage locations for water and include: ◦ Oceans, seas, and lakes. ◦ Rivers, glaciers, soil, and rocks. ◦ The atmosphere and living organisms. • Total Volume: The total amount of water on Earth does not change, even when it changes state, because it is constantly being replaced or recycled through the cycle. Main Processes and Energy Transfer The movement of water through the cycle is driven by energy (thermal energy from the Sun) and force (gravity and wind). • Energy Gain (Absorption): ◦ Melting: Water changes from a solid state (ice) to a liquid state and gains energy. ◦ Evaporation: Liquid water changes into a gas state (water vapor) by gaining thermal energy. ◦ Transpiration: A specialized type of evaporation occurring in plants where water vapor is released through tiny holes in leaves called stomata. Approximately 10% of water vapor in the air comes from transpiration. • Energy Loss (Release): ◦ Condensation: Water vapor (gas) cools down and changes back into liquid water, releasing energy. ◦ Freezing: Liquid water changes into a solid state (ice) and loses energy. • Other Key Steps: ◦ Precipitation: Water falls back to Earth as rain, snow, sleet, or hail (snow pellets). ◦ Runoff: Water flows over Earth's surface into streams, rivers, and eventually larger bodies of water like oceans. ◦ Collection: Rainwater is collected in different water bodies to start the cycle again. Forces Driving Water Movement • Gravity: The main force that pulls water downward. It is responsible for: ◦ Bringing precipitation (rain and snow) from clouds to the surface. ◦ Moving ice in glaciers from higher to lower elevations. ◦ Causing liquid water to flow downhill into rivers and seas. ◦ Leakage: Pulling liquid water down into the ground to reach groundwater reservoirs. • Wind: Another force that affects water movement and transports water to different locations on Earth. Atmospheric Processes • Cloud Formation: Water vapor attaches to particles such as dust or smoke in the air and condenses into tiny droplets. When millions of these droplets join, they become heavy and fall as rain. • Convection: The transfer of heat in liquids and gases. ◦ Warm air/liquid: Becomes less dense, lighter, and rises upward. ◦ Cold air/liquid: Is more dense, heavier, and moves downward to replace the warm fluid. ◦ This process leads to convection currents, which help determine regional climates and drive wind and ocean currents. Solar Radiation and Climate The amount of solar energy reaching Earth differs from place to place, which affects the weather: • Hottest Regions (Equator): Sun rays fall perpendicular (vertical). Heat is concentrated on a small area, making the weather hot. • Moderate Regions: Sun rays fall semi-inclined. Heat is distributed over a larger area, making the weather warm. • Coolest Regions (Poles): Sun rays fall very slanted (inclined). Heat is spread over a very large area, making the weather very cold. Earth's Wind System • Wind Formation: Wind is generated when warm air (heated by the Sun) rises and is replaced by cooler air flowing from nearby areas. • Factors Affecting Wind: The amount of solar radiation and the rotation of Earth determine global wind directions. • Global Wind Cycle: Unequal heating between the equator and the poles generates a constant wind system. Warm air rises at the equator and moves toward the poles, while cold air from the poles moves toward the equator. • Importance: If there were no wind, the equator would become extremely hot, the poles would freeze solid, and many ecosystems would disappear. Practical Examples • Turkey’s Salt Lake: High evaporation in the summer can turn this large lake into a small puddle or dry it up completely. It is a critical site for flamingos, which migrate there to breed and feed on algae in the shallow, warm water.

Weathering describes the breaking down or dissolving of rocks and minerals on the surface of the Earth. Water, ice, acids, salts, plants, animals, and changes in temperature are all agents of weathering. Once a rock has been broken down, a process called erosion transports the bits of rock and mineral away. No rock on Earth is hard enough to resist the forces of weathering and erosion. Together, these processes carved landmarks such as the Grand Canyon, in the U.S. state of Arizona. This massive canyon is 446 kilometers (277 miles) long, as much as 29 kilometers (18 miles) wide, and 1,600 meters (1 mile) deep. Weathering and erosion constantly change the rocky landscape of Earth. Weathering wears away exposed surfaces over time. The length of exposure often contributes to how vulnerable a rock is to weathering. Rocks, such as lavas, that are quickly buried beneath other rocks are less vulnerable to weathering and erosion than rocks that are exposed to agents such as wind and water, As it smoothes rough, sharp rock surfaces, weathering is often the first step in the production of soils. Tiny bits of weathered minerals mix with plants, animal remains, fungi, bacteria, and other organisms. A single type of weathered rock often produces infertile soil, while weathered materials from a collection of rocks is richer in mineral diversity and contributes to more fertile soil. Soils types associated with a mixture of weathered rock include glacial till, loess, and alluvial sediments. Weathering is often divided into the processes of mechanical weathering and chemical weathering. Biological weathering, in whichliving or once-living organisms contribute to weathering, can be a part of both processes. Mechanical Weathering Mechanical weathering, also called physical weathering and disaggregation, causes rocks to crumble. Water, in either liquid or solid form, is often a key agent of mechanical weathering. For instance, liquid water can seep into cracks and crevices in rock. If temperatures drop low enough, the water will freeze. When water freezes, it expands. The ice then works as a wedge. It slowly widens the cracks and splits the rock. When ice melts, liquid water performs the act of erosion by carrying away the tiny rock fragments lost in the split. This specific process (the freeze-thaw cycle) is called frost weathering or cryofracturing. Figure 4.3 Frost Wedging Temperature changes can also contribute to mechanical weathering in a process called thermal stress. Changes in temperature cause rock to expand (with heat) and contract (with cold). As this happens over and over again. the structure of the rock weakens. Over time, it crumbles. Rocky desert landscapes are particularly vulnerable to thermal stress. The outer layer of desert rocks undergo repeated stress as the temperature changes from day Eventually, Lo outer night. layersflake off in thin sheets, a process called exfoliation. Exfoliation contributes to the formation of bornhardts, one of the most dramatic features in landscapes formed by weathering and erosion. Bornhardts are tall, domed, isolated rocks often found areas. in tropical Sugarloaf Mountain, an iconic landmark in Rio de Janeiro, Brazil, is bornhardt. a Salt also works to weather rock in a process called haloclasty. Saltwater sometimes gets into the cracks and pores of rock. If the saltwater evaporates, salt crystals are left behind. As the crystals grow, they put pressure on the rock, slowly breaking it apart. Plants and animals can be agents of mechanical weathering. The seed of a tree may sprout in soil that has collected in a cracked rock. As the roots grow, they widen the cracks, eventually breaking the rock into pieces. Over time, trees can break apart even large rocks. Even small plants, such as mosses, can enlarge tiny cracks as they grow. Animals that tunnel underground, such as moles and prairie dogs, also work to break apart rock and soil. Other animals dig and trample rock aboveground, causing rock to slowly crumble. Chemical Weathering Chemical weathering changes the molecular structure of rocks and soil.For instance, carbon dioxide from the air or soil sometimes combines with water in a process called carbonation. This produces a weak acid, called carbonic acid, that can dissolve rock. Carbonic acid is especially effective at dissolving limestone. When carbonic acid seeps through limestone underground, it can open up huge cracks or hollow out vast networks of caves. Carlsbad Caverns National Park, in the U.S. state of New Mexico, includes more than 119 limestone caves created by weathering and erosion. The largest is called the Big Room.. With an area of about 33,210 square meters (357,469 square feet), the Big Room is the size of six football fields. Another type of chemical weathering works on rocks that contain iron. These rocks turn to rust in a process called oxidation. Rust is a compound created by the interaction of oxygen and iron in the presence of water. As rust expands, it weakens rock and helps break it apart. Another familiar form of chemical weathering is hydrolysis. In the process of hydrolysis, a new solution (a mixture of two or more substances) is formed as chemicals in rock interact with water. In many rocks, for example, sodium minerals interact with water to form a saltwater solution. Hydration and hydrolysis contribute to flared slopes, another dramatic example of a landscape formed by weathering and erosion. Flared slopes are sometimes nicknamed "wave rocks." Their c-shape is largely concave rock formations a result of subsurface weathering, in which hydration and hydrolysis wear away rocks beneath the landscape's surfaceWeathering and People Weathering is a natural process, but human activities can speed it up. For example, certain kinds of air pollution increase the rate of weathering Burning coal, natural and petroleum releases chemicals such as nitrogen oxide and gas, sulfur dioxide into the atmosphere. When these chemicals combine with sunlight and moisture, they change into acids. They then fall back to Earth as acid rain. Acid rain rapidly weathers limestone, marble, and other kinds of stone. The effects of acid rain can often be seen on gravestones, making names and other inscriptions impossible to read. Acid rain has also damaged many historic buildings and monuments. For example, at 71 meters (233 feet) tall, the Leshan Giant Buddha at Mount Emei, China is the world's largest statue of the Buddha. It was carved 1,300 years ago and sat unharmed for centuries. An innovative drainage system mitigates the natural process of erosion But in recent years, acid rain has turned the statue's nose black and made some of its hair crumble and fall.

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