While avalanches are sudden, the warning signs are almost always numerous before they let loose. Yet in 90 percent of avalanche incidents, the snow slides are triggered by the victim or someone in the victim's party. Avalanches kill more than 150 people worldwide each year. Most are snowmobilers, skiers, and snowboarders. TYPES OF AVALANCHES Many avalanches are small slides of dry powdery snow that move as a formless mass. These "sluffs" account for a tiny fraction of the death and destruction wrought by their bigger, more organized cousins. Disastrous avalanches occur when massive slabs of snow break loose from a mountainside and shatter like broken glass as they race downhill. These moving masses can reach speeds of 80 miles (130 kilometers) per hour within about five seconds. Victims caught in these events seldom escape. Avalanches are most common during and in the 24 hours right after a storm that dumps 12 inches (30 centimeters) or more of fresh snow. The quick pileup overloads the underlying snowpack, which causes a weak layer beneath the slab to fracture. The layers are an archive of winter weather: Big dumps, drought, rain, a hard freeze, and more snow. How the layers bond often determines how easily one will weaken and cause a slide. Storminess, temperature, wind, slope steepness and orientation (the direction it faces), terrain, vegetation, and general snowpack conditions are all factors that influence whether and how a slope avalanches. Different combinations of these factors create low, moderate, considerable, and high avalanche hazards. WHAT TO DO IN AN AVALANCHE If caught in an avalanche, try to get off the slab. In most instances, this is not easy. Skiers and snowboarders can head straight downhill to gather speed, then veer left or right out of the slide path. Snowmobilers can punch the throttle to power out of harm's way. No escape? Reach for a tree. No tree? Swim hard. The human body is three times denser than avalanche debris and will sink quickly. As the slide slows, clear air space to breathe. Then punch a hand skyward. Once the avalanche stops, it settles like concrete. Bodily movement is nearly impossible. Wait—and hope—for a rescue. Statistics show that 93 percent of avalanche victims survive if dug out within 15 minutes. Then the survival rates drop fast. After 45 minutes, only 20 to 30 percent of victims are alive. After two hours, very few people survive. Avalanche Safety Tips Avalanches can occur without warning, sending thousands of tons of debris and ice downhill at breakneck speeds. Every year, hundreds of people—usually skiers, snowboarders, or snowmobilers—get caught in avalanches. Here are some key steps you can take to avoid avalanches and actions to take if you or someone you're with gets caught in a snowslide. PREPARATION •Wear an avalanche rescue beacon that signals your location. • Learn how to use the rescue equipment. • Practice using the rescue equipment. AWARENESS • Constantly evaluate avalanche conditions. • Areas with fresh accumulations of wind-driven snow are particularly vulnerable. • Extremely steep slopes particularly in shaded areas near a ridge are also risky. • Always travel with a partner. Descend risky areas one by one and watch for avalanche signs. WHAT TO DO IF CAUGHT • If caught in a slide, try to get off the slab or grab a tree. • If swept away, swim to the surface. RESCUE • Carry a small shovel and a long probe to locate a buried partner. • Evaluate the avalanche hazard before attempting a rescue.
CAPE TOWN DROUGHT: http://www.independent.co.uk/travel/news-and-advice/cape-town-drought-water-shortage-tourists-reservoir-south-africa-a8175686.html
A tsunami is a series of ocean waves that sends surges of water, sometimes reaching heights of over 100 feet (30.5 meters), onto land. These walls of water can cause widespread destruction when they crash ashore. WHAT CAUSES A TSUNAMI? These awe-inspiring waves are typically caused by large, undersea earthquakes at tectonic plate boundaries. When the ocean floor at a plate boundary rises or falls suddenly, it displaces the water above it and launches the rolling waves that will become a tsunami. Most tsunamis–about 80 percent–happen within the Pacific Ocean’s “Ring of Fire,” a geologically active area where tectonic shifts make volcanoes and earthquakes common. Tsunamis may also be caused by underwater landslides or volcanic eruptions. They may even be launched, as they frequently were in Earth’s ancient past, by the impact of a large meteorite plunging into an ocean. Tsunamis race across the sea at up to 500 miles (805 kilometers) an hour—about as fast as a jet airplane. At that pace, they can cross the entire expanse of the Pacific Ocean in less than a day. And their long wavelengths mean they lose very little energy along the way. In deep ocean, tsunami waves may appear only a foot or so high. But as they approach shoreline and enter shallower water they slow down and begin to grow in energy and height. The tops of the waves move faster than their bottoms do, which causes them to rise precipitously. WHAT HAPPENS WHEN IT HITS LAND A tsunami’s trough, the low point beneath the wave’s crest, often reaches shore first. When it does, it produces a vacuum effect that sucks coastal water seaward and exposes harbor and sea floors. This retreating of sea water is an important warning sign of a tsunami, because the wave’s crest and its enormous volume of water typically hit shore five minutes or so later. Recognizing this phenomenon can save lives. A tsunami is usually composed of a series of waves, called a wave train, so its destructive force may be compounded as successive waves reach shore. People experiencing a tsunami should remember that the danger may not have passed with the first wave and should await official word that it is safe to return to vulnerable locations. Some tsunamis do not appear on shore as massive breaking waves but instead resemble a quickly surging tide that inundates coastal areas. The best defense against any tsunami is early warning that allows people to seek higher ground. The Pacific Tsunami Warning System, a coalition of 26 nations headquartered in Hawaii, maintains a web of seismic equipment and water level gauges to identify tsunamis at sea. Similar systems are proposed to protect coastal areas worldwide. Tsunami Safety Tips Here are some measures you can take to avoid trouble if you're caught in a tsunami. HOW TO PREPARE
ONCE IT HITS • Never stay near shore to watch a tsunami come in. • A tsunami is a series of waves. Do not return to an affected coastal area until authorities say it is safe. Gene
•Basic physical and functional unit of heredity •Made up of DNA •Each person has 2 copies of each gene, one inherited from each parent. DNA •Deoxyribonucleic Acid or DNA •Contains the instructions an organism needs to develop, live, and reproduce •Found inside every cell •Passed down from parents to children (offspring) Chromosomes •Thread-like molecules that carry heredity information •Made of protein and one molecule of DNA •Most have arranged pairs within the nucleus of the cell X/Y Chromosomes •Each person has one pair of sex chromosomes in each cell. •Females have two X chromosomes. •Males have an X and Y chromosome. •The Y chromosome contains a gene, which triggers embryonic development to become a male. Cell •Smallest structural, functional, and biological unit of all living organism •Often called the “building blocks of life” •Nucleus – organelle present in most eukaryotic cells – contains genetic material Asexual Reproduction •Type of reproduction by which offspring arise from a single organism •Produced by mitosis •Offspring inherit the genes of only one parent •The offspring is genetically identical (uniform)of the parent. Mitosis •Type of cell division •Results in two daughter cells having the same number and kind of chromosomes as the parent cell •Cell goes through different phases before becoming clones of parent Types of Asexual Reproduction •Binary Fission •Budding •Fragmentation •Regeneration Vegetative Reproduction Binary Fission •Common in prokaryotes (organisms with no nucleus) •Occurs in some single-celled eukaryotes (with a nucleus) •Fully grown parent cell splits into two halves, producing two new cells •Examples: bacteria and amoeba, and euglena Budding •Offspring grows out of the body of the parent (buds) •Example: hydras Fragmentation •The body of the parent breaks into distinct pieces •Each piece can produce an offspring •Example: planarians Regeneration •If a piece of a parent is detached, it can grow and develop into a completely new offspring. •Example – some starfish Vegetative Reproduction •A process by which new organisms arise without production of seeds or spores •Example: some plants, potatoes Advantages of Asexual Reproduction •Good for organisms that are not mobile and cannot look for a mate •Numerous offspring without “costing” the parent great amount to energy •Quick Disadvantages of Asexual Reproduction •Lacks genetic variation •Because organisms are the same, they share the same weaknesses •If the environment changes, there may not be time to adapt quickly enough to survive. Sexual Reproduction •Type of reproduction by which offspring arise from two parents. •The male produces male gametes or sperm. •The female produce female gametes or ovum. •Gametes (sex cells) are formed by meiosis. Meiosis •A type of cell division that reduces the number of chromosomes in the parent cell by half and produces four gamete cells. •Goes through many phases •Required to produce egg and sperm cells for sexual reproduction Mitosis vs Meiosis •Mitosis produces 2 diploid cells, which are identical to the parents. (uniform) •Meiosis produces 4 haploid cells, which contain some characteristics of the parent cell but are not identical. (diverse) Sexual Reproduction •A sperm enters an ova during fertilization. •Each gamete contains 23 pairs of chromosomes. •The two fuse to form a zygote with 46 pairs of chromosomes. •Offspring appearance vary due to new combinations of genes. •The zygote then divides by mitosis •It passes through different developmental phases to transform into a multicellular individual •The offspring are genetically different (not identical) to their parents Advantages of Sexual Reproduction •Leads to genetic variations in new generations, which is fundamental for environmental adaptation •Organism is more protected – does not necessarily have the weakness of parent •Removes bad genes from the population Disadvantages of Sexual Reproduction •Organism must find a mate •Takes longer time to reproduce •Can prevent favorable genes from being passed down •Produces fewer offspring Some Organisms Reproduce Both Ways •Some plants and animals can reproduce both ways •There are benefits to this adaptation. What might they be? •Plant examples: fungi, strawberries, daffodils •Animal examples: starlet sea anemone, jellyfish, sponges Mutations •A change that occurs in the DNA sequence •Causes changes in an organism – its appearance, how it behaves, and how it functions •Mutations are essential to evolution – the raw material of genetic variation Harmful Mutations •Sickle cell anemia •Cystic Fibrosis •Albinism •Wingless Fruit Fly •Hemophilia Mutations •Sickle cell anemia is a genetic disease with severe symptoms •Caused by a the mutation of the gene that helps make hemoglobin (carries O2 to red blood cells) •The “R” is the dominate gene and the “r” recessive
Convection Currents
•Heat energy transfer between two parts of a fluid of different temperatures •When hot fluids rise and cold fluids sink •Occurs in the atmosphere •Occurs in the oceans •Occurs in planetary mantles •It also occurs in soup Earth’s Mantle •Convection currents flow within the mantle •Causes the tectonic plates to move •Less dense hot magma moves upward •More dense cooler magma moves downward Earth’s Oceans •Convection currents flow within the oceans •Temperature (solar heating) and salinity affects the density of water creating global currents. •More dense water sinks •Less dense water rises Earth’s Atmosphere •Solar radiation heats the Earth’s surface •That heat is transferred to the air by conduction •Air touching the Earth’s surface expands, becomes less dense and rises. •Air cools as it gets higher into the atmosphere. •Cool air becomes more dense and sinks. •Wind is created as the cool air moves in to replace the warm air. High pressure (H) •As air masses cool, they becomes more dense and sinks toward the Earth’s surface. Low pressure (L) •As air masses warm, they becomes less dense and rises above the Earth’s surface Wind •The pressure difference between a high pressure area and its lower pressure surroundings cause a wind to develop •Flows from higher to lower pressure Earth’s atmospheric convection currents cause •Global winds •Local breezes •Cyclones (Hurricane/Typhoon) •Thunderstorms Local Breezes Sea breeze •Gentle wind that flows from the cool air over the water(high pressure) toward the warm air over the land (low pressure). •During the day solar radiation heats the land more quickly than water. Land breeze •Breeze that flows form the cool air above land (high pressure)toward the warmer air above the water (low pressure). •Caused by land cooling more quickly than water in the evening. Valley breeze •During the day, the surface of the mountain heats the air high up in the atmosphere, quicker than the valley floor heats. •This attracts the air from the valley, creating a breeze that blows from the valley floor(high pressure) up towards the top of the mountain (low pressure). Mountain breeze •In the evening, the mountain slopes cool the surrounding air more quickly than the air found lower in the atmosphere. •This causes winds to blow down the mountain (high pressure)towards the valley floor (low pressure).
https://youtu.be/5sg9sCOXFIk
https://www.youtube.com/watch?v=5sg9sCOXFIk
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Erik E. Mason
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