Hi there! I’m doing a special blog post for Halloween but it’s a little late. Hope you enjoy anyway!
In Austria, some people will leave bread, water, and a lighted lamp on the dinner or kitchen table when they go to bed at night. The reason why they leave bread, water, and a lighted lamp on a dinner or kitchen table is that they believed by doing so the objects on the table would welcome the dead souls back to earth for this particular night is a night of strong cosmic energies. In Austria, Catholics celebrate the entire portion between October 30 and November 8 as Seleenwoche or All Souls’ Week.
On All Saints’ Day, Catholics attend church services in honor of the saints, the martyrs and those who have died for the Catholic faith. Some people may also visit their family’s graves to beautify the graves with wreaths and small lanterns. Sometimes, a mass is said at the gravesite and the grave is sprinkled with holy water.
On November 2nd which is All Souls’ Day, Catholics attend a special Requiem masses, where they can remember the people who may be close to them that have died. Prayers for the dead are said and votive candles are lit to honor their memories. In Belgium, people believed that it was bad luck for a black cat to cross your way.
Some people believed that it was unlucky for a black cat also to come into their homes or travel on their ships. In Belgium, people light candles in memory of their spiritless relatives. In Great Britain, everyone wants to welcome the friendly spirits with special soul-cakes for them.
When children in costumes called upon their neighbors’ homes on Halloween they would be given soul-cakes also! In some parts of Britain, Halloween was known as Mischief Night in the past. It was a night for mischief making.
People would take the doors off their hinges on that night. The doors were often tossed into ponds, or taken a long way away. In England, it is said that elves rode on the backs of the villagers’ cats. The cats had fun but the villagers didn’t and would lock their cats up so that the elves couldn’t catch the cats.
Children were told not to sit in the circles of yellow and white flowers where fairies have danced as they may be stolen by the fairies. It was also considered bad to sit under the hawthorn tree because the fairies loved to dance on the hawthorn tree and if the children saw them, their tempers would be prickled. In England, the black cat was considered to be good luck and a white cat was considered to be bad luck.
In England, children make punkies out of large beets. The children cut out a design of their choice into the beet. The children carry them through the streets and sing the Punkie Night Song afterward.
The children knock on doors and ask for money. In some parts of England, turnip Lanterns are placed on gateposts to protect homes from the evil spirits. In England, Halloween was nicknamed, Nutcracker Night or Snap Apple Night.
Families would sit before a great fire in the hearth, roasting nuts and eating apples. The families told stories and played holiday games. It was an evening of great fun and merriment.
In England, they continued to practice their deep-rooted, ancient pagan rites well after the arrival of Christianity in the middle of the sixth century. The Church fathers had become concerned that the popularity of non-Christian festivals was growing at the expense of Christian holy days. Pope Gregory I, in 601 issued a decree to his missionaries about the faith and customs of the people whom he wanted to convert to Christianity.
Gregory knew that it would be impossible to eradicate the beliefs of the natives totally and so suggested to his priests that they convert them whenever possible. If the native people worshipped at a well, or sacred grove, Gregory informed his missionaries to enshrine them to Christ and let the worship continue. Gregory’s successor Pope Boniface IV in 609, declared May 13 All Saints’ Day.
Unfortunately, while pagans were happy to add All Saints’ Day to their calendar, they were unwilling to give up their existing festival of the dead and continued to celebrate Samhain. Intent on eliminating the ongoing power of the pagan beliefs, Pope Gregory III followed in the footsteps of the earlier Christian leaders and intentionally united the Christian All Saints’ Day to the festival of Samhain. He then moved All Saints’ Day to November 1, which became more commonly known as All Hallows.
Because Samhain had traditionally fallen the night before All Hallows, it eventually became known as All Hallows’ Even’ or Halloween. Previous church leaders to Gregory III discouraged the Samhain tradition of wearing frightening costumes, but Gregory decided to allow people to dress up in honor of the saints. Other traditions, such as begging for food and kindling, were made legal by the Church, providing that any food that was given to the beggars would be given to the poor, rather than to appease the evil spirits.
The Church also added a second day to the festival that fell on November 2 and was called All Souls’ Day and was dedicated to the souls of those who are still left in purgatory. These souls had to endure the punishment of purgatory for their sins. It is believed that the lighting of candles and the saying of prayers for the dead would shorten the time they were to suffer in purgatory before they would rise to heaven.
The tradition of begging for food soon was replaced with souling or Soul Caking. The idea was for children to go from door to door asking for money to give to the poor and a soul cake to have for themselves. Every cake they would receive, the children would say a prayer for the souls of the dead.
Soul cakes were called several different names throughout England such as Saumas or soul mass cakes which were dark fruitcakes, another cake was covered in caraway seeds and made into a bun. In North England, the tradition of lighting bonfires was central to the Halloween celebration. Superstition was still very strong as a result of the aftermath of the witch-hunts; witches were believed to take to the air to harass everyone at Halloween.
Halloween was called Tan Day for the township of Lancashire. Tan Day was named as it was the Celtic tein, or fire and pitchforks full of burning hay were flung into the air to scare the witches. Another reason was the heat and the smoke of the bonfires would also drive away any airborne witches.
In Canada, people welcome trick-or-treaters by placing pumpkins called jack-o’-lanterns in their windows. Also in Canada, it is bad luck for a black cat to cross your path, enter your home, or even enter your ship. In Canada, people give trick-or-treaters treats to make sure they are not being played a trick on.
Children also make Jack-o’-lanterns for Halloween. Dressing up as witches, ghosts and beasts for trick-or-treating is done also. It was believed these costumes would protect people from bad luck.
Thousands of years ago there was a tribe of farmers called the Celts. They knew that the sun helped make their crops grow, so when autumn came the sun began to fade and they believed that the sun would be winter’s prisoner for six months. They were worried that the sun would not return so to make sure it did they held a festival on October 31.
During which, they asked the sun to return safely in the summer. All the cooking fires were put out and a huge bonfire was lit on the hillside. Here they prayed the sun would shine brightly after winter was over.
The next morning, they would return to the hillside take a piece of the burning wood from the remains of the bonfire and light new fires so as to bring good luck. Feasts were held over the new fires and people would dress up in costumes made out of animal skins. It was believed these costumes would protect people from bad luck.
This is how Halloween is said to have begun and is still celebrated today. Cats were considered by the Celts to be spirits and that cats could predict the future. In Ireland, the black cat was considered to be bad luck and if it crosses your path while walking or crosses the threshold of your home or ship it was considered bad luck.
In Ireland, children would cut scary faces into hollowed-out turnips, large rutabagas, or potatoes. Then place a candle inside them. Children once enjoyed throwing cabbages and turnips at doors at Halloween time.
Smashing bottles near windows was also done for fun. The Celts referred to Halloween as The Samhain Festival. It was during this time that you would lead your livestock home from summer pastures to the winter shelters.
Samhain Eve was a time when the veil between the worlds of the living and the dead grew thinner, and ghosts ventured toward the warmth if people’s homes and hearths. On the Eve, the Celts built bonfires in memory of their departed ancestors and left food and drinks on their tables overnight for eating by the ghosts. The tenth-century abbot of Cliny Odile changed Samhain’s name to All Saints’ Day.
October 31 became All Hallows’ Eve or Hallowes’ Even, and eventually would become Halloween. Halloween is now for the children, whose practice of trick-or-treating has its roots in the English custom of soul-caking. From medieval times onward, poor people would beg door-to-door for spiced cakes that the householders would award as payment for prayers the beggars promised to say for the householders’ ancestors.
This song was referred to as the soul-cakers song. In Ireland, they continued to practice their deep-rooted, ancient pagan rites well after the arrival of Christianity in the middle of the sixth century.
The Church fathers had become concerned that the popularity of non-Christian festivals was growing at the expense of Christian holy days. In China, the Halloween festival is known as Teng Chieh in which food and water are placed in front of photographs of relatives of people. Bonfires and lanterns are lit to light the spirits path back to earth.
Another Halloween festival is called The Feast of the Hungry Ghosts. In China, the souls of the dead, particularly
during the seventh lunar month, wander the earth in search of affection. They are known as the hungry ghosts because of their hunger for recognition and care.
The number of souls is usually increased by those who died unnatural deaths, and who may not have been given a proper burial or burial place which their families could visit in order to pay them respect. Other such Hungry ghosts that are abroad during this month are the spirits of people whose families had either died out or who showed no concern for their welfare in the beyond. Bereft of comfort, they feel abandoned and, lacking ancestral worship, may turn malignant and become powerful threats to the living.
The purpose of the Festival of the Hungry Ghosts, is dedicated to the earthbound spirits. It’s purpose is to make them feel welcome and to satisfy their spiritual hunger. This will placate any possible anger they might have and gain their gratitude.
In the sacred ritual of the day, the spirits are offered joss sticks, food and gifts. The gifts that are made of paper represent objects with which they were familiar while on earth and are intended to make them feel at home. Paper money is burnt on their behalf, to pay for their expenses in the netherworld.
Fires are lit to light the way for the hungry ghosts and a gesture of welcome. In Czechoslovakia, chairs are placed by the fireside. There is a chair for each family member and one for each family member’s spirit.
In Germany, people put their knifes away. This has to be done so they don’t risk hurting the returning spirits.
In the regions of Bavaria, Austria, and Southern Germany, Catholics celebrate the entire period between October 30 and November 8 as Seleenwoche or All Souls’ Week. In Hong Kong, there is a festival similar to Halloween.
During the Hungry Ghosts Festival or Yue Lan, ghosts and spirits roam the world for 24 hours. Some people burn pictures of fruit or money. This was believed to reach the spirit world and comfort the ghosts on this day.
In Italy, they make cakes in the shape of beans. These cakes are called Beans of the Dead. In Southern Italy, families prepare a special feast for the souls of the departed on All Souls’ Day.
When the family came home to find that their offerings hadn’t been consumed it meant that the spirits disapproved of their home and would work evil against them during the coming year. In Italy, November 1 has become a public holiday. In Japan, O-Bon festival celebrates the memory of the dead relatives.
Food and water is placed in front of photos of the dead. Bonfires and lanterns light the spirits’ path back to earth. O-Bon celebrated by some people from July 13-15 and others from August 13-15, O-Bon gets its name from the Sanskrit word for “to hang upside down.”
It refers to a legend about a Buddhist monk who is deep in meditation was able to see his long-lifeless mother hanging upside down in the Buddhist equivalent of misery. This was her punishment for eating meat during her lifetime which is a Buddhist taboo and refusing to repent of it. The monk was holy enough to go to misery and buy his mother’s passage to Nirvana with some of his own excess goodness.
On the first day of O-Bon, people decorate their loved ones’ graves with fruit, cakes, and lanterns. On the second day, spirit altars or they are referred to tamadana are assembled at home. Atop a woven rush mat stand the ancestors’ memorial plaques, tempting vegetarian dishes, and cucumbers carved to represent horses on which the spirits are invited to ride.
On the third day, whole communities gather for the bon-odori, a hypnotic, slow dance that moves in concentric circles or multiple lines. Hundreds of people often dance together. As evening falls, tiny paper lanterns are set adrift on river or sea: these omiyage gently light the spirits way back to the other shore.
Buddhist Japanese remember their dead at the time in autumn of equal days and nights. The festival that is celebrated is called Higan. It is a time when people visit the graves of friends and family who are dead.
They tidy up the area and think about the dead people. In Mexico, they have picnic lunches on the graves of their relatives. As this is a day of remembrance, happiness and celebration.
They bake bread and make candy in the shape of skull and crossbones, a casket, or a skeleton. The children run through the streets with lanterns and ask for coins. People light bonfires, set off firecrackers, and hang lanterns on trees to guide the souls of the dead home.
In Mexico, All Saints’ Day is devoted to all the departed children. This is a prelude to November 2’s Dia de los Muertos, Day of the Dead which is a national holiday on which all the grown-up ghosts will be arriving in full force. The littler ghosts get a head start.
To help them find their way back to the homes where they once lived, parents and still alive family members often shoot off firecrackers. In some parts of Mexico on this night, they strew a path of flower petals from the graveyard to the front porch. Mexico’s Day of the Dead calls for happy all day picnics beside the graves of dead relatives.
At home, people assemble little altars called ofrendas, stocked with the departed loved ones favorite foods and drinks, their photos, and other memories, as well as candles and pungent marigolds, a flower long associated with death. The Mexican custom of Erecting Day of the Dead altars has caught on north of the border, where the altars serve as the focus of ancestor rituals and memorials.
In Mexico, October 27 is the Feast of the Holy Souls or Fiesta de las Santas Animas, families begin the fiesta by cleaning their relatives’ graves and adorning them with pine needles and flowers. The families assemble a temporary altar near the gravesite, stocking the altars with candles and all kinds of foods such as meat, beans, chilies, salt, tortillas, fruit and sometimes adult beverages. Each person in the family then takes turns in talking to the departed spirit, offering it the food and assuring it that it is loved.
The ceremonies go on for several days, as every family has more than one grave to attend to. In the United States, trick-or-treaters are welcomed by placing lighted pumpkins known as jack-o’-lanterns in their windows. The North American tradition of trick or treat comes from the original idea that you must be kind to dead ancestors or they will play a trick on you.
Neopagans of North America honor their ancestors on October 31. It was once believed that on this night any souls who had not yet passed into the paradise of the summer lands might return to wander the streets and visit their old homes once more. Neopagans celebrate the festival today as a turning point between the old and the new year, as well, the date of October 31 as the gateway between the worlds.
Many neopagans also believe that on the eve of Samhain, the veil that separates each world that of the living and that of the dead is at its thinnest and that on this night, there is a better chance of being successful in communicating with their ancestors. In the Philippines, people will light candles in the memory of their dead relatives. In Poland, doors and windows are left open to welcome the spirits or the visiting souls.
In Portugal, they have feasts of wine and chestnuts at the cemetery. In Portugal, they bake special sugar cakes with cinnamon and herb flavoring. Parentalia the Roman holiday dedicated to honoring dead family began precisely at the sixth hour on the thirteenth day of February and lasted a full nine days afterward.
These English parental days weren’t a spooky time for the average Roman citizen. Rather, these were days of obligation and feasting, quiet and respectful, introspective, like a wake. During the Parentalia, all temples were closed, weddings were forbidden, and governmental magistrates uncharacteristically appeared in public devoid of the insignia of their office.
People visited their parents’ and other relatives’ graves, bringing objects such as milk, wine, honey, oil, and spring water. Some brought sacrificial blood from the bodies of black animals. They decked the graves with roses and violets.
Dining with the dead at the grave site, the celebrant would offer the traditional greeting and farewell of the holiday which is Salve, sancte parens and Hail, holy ancestor. The Vestal virgins, the priestesses who tended the goddess Vesta’s shrine in the Forum performed rites of their own at the Parentalia. The senior Vestal paid a ceremonial visit to the group’s parental tomb which was the early Vestal, Tarpeia.
On May 9 is the Lemuria a festival held to remove the more hungry ghosts. The Lemuria is a festival held for homeowners to rid their homes of resident lemures. A celebrant would walk through the house barefoot at midnight walking from room to room with one hand upheld in the fig gesture which is the thumb held between the second and third fingers.
The celebrant’s mouth would be filled with dried black beans which he would spit out one by one as he walked. The beans were used as ghost bait. As he walked he would spit a black bean out and say the chant nine times: With these I redeem myself and mine.
The idea was that the lemures would be following him, eating the beans that had been spat out by the celebrant. While the celebrant was walking around with the ghosts following him people weren’t to look back during the ritual. Once the celebrant had come full circle, he would wash his hands thoroughly then he would beat brass pans together making as much noise as possible so as to bid the lemures leave.
A festival held called Feralia is much like the Day of the Dead ceremony. The name feralia comes from the verb ferre meaning to carry, or to ferry. The Roman families would go to the ancestral graveyard, ferrying offerings.
The reasons was that they believed the ghosts were hovering around the graves, so they take food to extinguish the pyres. Once the ancestors were honored and fed, comes the ceremony Caristia from the word Cara meaning dear. This was a holiday to re-affirm, a day of affectionate family reunions.
All fighting was forbidden, old feuds would be forgotten, and sibling rivalries would have to be set aside. In Russia, the blue cat is said to bring good luck. Blue cats like the Russian Blue, British Blue and Burmese.
In Scotland, Soul Cakes were known as Dirge Loaves and were flat, round buns of oat flour. Scottish superstitions ran deeper and darker than most. In memory of the fact that Scotland had been the only country to burn to death its supposed witches, children in Aberdeenshire would run around their villages, banging on doors and shouting.
This practice continued until the early twentieth century. Effigies of witches were burned on the Halloween bonfire. A dummy of an old woman called the shandy Dan was wheeled in a cart to the center of a large gathering of villagers and then tossed onto the fire with much celebration.
They also smashed bottles near windows. March 13-19 in Spain is Las Fallas which is in honor of St. Joseph whose feast day is on March 19. There are fireworks, bullfights, music, costumed revelers and parades.
Giant models of people or papier-mâché effigies called ninots are stuffed with fireworks and burned. The bonfires and burning of effigies is done to blazing away the last vestiges of winter and welcoming the glow of the summer Sun. In Australia, they celebrate Guy Fawkes Eve as the day for Halloween or as it is also known Mischief Night or Danger Night.
On this night, it is a day for children to create mischief by doing tricks or getting a treat. It is not widely done in Australia as it is in America and elsewhere, in fact most children in Australia celebrate it as dancing at their schools or in other activities. Not as a day to create lawless or other mischief.
In Estonia, folktales tell of unsuspecting people who wander into village churches on All Saints’ Day night only to find all the pews filled with ghosts who sit and kneel attentively while a ghostly priest celebrates mass at the altar. French bellmen would walk through the streets warning of the arrival of, “The spirits are about to arrive!” Once everyone heard this they would all hurry to bed and shut their eyes.
Today, the French children beg for flowers with which to decorate churches and the graves of loved ones. In Guatemala, the advent season is a time of men dressing up as the devil in costumes playfully chasing children through the streets. To bring the season to a close on December 7, people are to light bonfires in front of their homes.
They would toss accumulated garbage and other debris onto these. In the City, fireworks explode into the night. This event is called the Burning the Devil or La Quema del Diablo.
Saint Martin’s Day, November 11th, is a celebration in Holland has a lot in comparison to “trick-or-treating”. People in Holland go around getting treats by ringing on some doorbells, singing songs for which they are given sweets or tangerines. They go around with lanterns and here is one of the songs they sing:
Elf November is de dag,
Dat mijn lichtje,
Dat mijn lichtje.
Elf November is de dag,
Dat mijn lichtje branden mag.
Those were the words to the Sint Maarten Song. This is the story of why the Dutch celebrate Saint Martin. It was a dark and stormy night.
Martin was quite alone on that dark stormy night. He only had a cloak and a singular piece of bread. He was returning home when suddenly a poor and homeless man appeared in the darkness.
Martin felt pity for the man and gave him half his piece of bread, and half his cloak and offered him hospitality in his home. Now he is called Saint Martin and is known for his kindness to the stranger. That is why they celebrate Saint Martin’s Day.
It is popularly a night for mischief and is called Mischief Night or Danger Night, which is on November 5th. The Odo Festival is held to mark the return of the dead which is the Odo to those still living, this occurs in the village of Igbo, Nigeria. The festival has three stages.
The first stage is observed with ritual celebrations and festivities to welcome those returning from the spirit world. The spirits stay for six or more months. Their departure is an emotional affair as they will not return for two years.
There are Odo plays featuring different characters in costumes. Most roles are by men with women as chorus members and as spectators. Children in Sicily go to bed on November 1 well aware that outside, in all the graveyards, the dead are rising from their tombs and coming like Santa Claus to deliver candies, cookies, and gifts to leave for them in celebration of All Saints’ Day.
On All Souls’ Day, the Sicilian chefs mark the holiday with almond-flavored “bones of the dead”, bone-shaped biscotti, with molded-sugar dolls, and with fave dei Morti, little Venetian cookies in the shapes of fava beans, a legume associated since ancient times with rites of the dead. Vu-Lan or Wandering Souls’ Day is a festival celebrated by all Vietnamese. When a person dies, it is believed their soul goes to inferno where it is judged and, depending on the person’s behavior on earth, is sent to heaven or kept in inferno.
Souls in inferno can gain release by the prayers of the living. Wandering Souls’ Day is the best time for these rituals. Inferno’s gates are opened at sunset and the bare hungry souls fly out, returning to the family altars.
Tables are spread with a meal for the ancestors and ‘wandering souls’, and incense sticks and votive papers are burned. This takes place in large rooms or outdoors so there is plenty of room for the ‘wandering souls’ who have no relatives, or whose relatives have forgotten them. In Wales, people build Halloween fires on the Vigil of Samhain.
The celebration is very somber. Each of the family is to write his or her name on a white stone which is then thrown in the fire. Then all of the family members march around a fire, praying for good fortune.
The next morning, after the fire has died out, each member sifts through the ashes to search for the stone. If any stone is missing, it means that the spirits will call upon the soul of that person during the coming year.
Hey there! I’m researching rocks because I’m curious about them. I also like rocks because they are so interesting. Enjoy!
Geologists define rocks as aggregate of minerals. Minerals are naturally occurring, not unhealthy substances with specific chemical compositions and structures. A rock can be filled of many crystals of one or more minerals, or combinations of many minerals. Several exceptions, such as coal and obsidian, are not composed of minerals but are thought to be rocks.
People often use rocks for include building materials, roofs, sculpture, jewelry, tombstones, chalk, coal for heat, and more. Oil and natural gas can also be found in rocks. Many metals like a fork are made from rocks known as ores. Even, prehistoric humans used rocks as early as 2,000,000 B.C. Flint and other hard rocks were very important raw materials for crafting arrowheads and other special natural made rocks.
Around 500,000 B.C., rock caves and structures made from stones had become important forms of shelter for early man. During that time, early men had learned to use fire, a development that allowed humans to cook food as needed to survive and greatly expand their geographical range. Eventually, most likely no sooner than 5000 B.C., humans had realized that minerals such as gold and copper could be from rocks. Tons of ancient monuments were crafted from stone, including the pyramids of Egypt, built from limestone about 2500 B.C., and the buildings of Chichen Itza in Mexico, also of limestone, built near A.D. 450.
Since the 1500s, scientists have studied minerals and mining, fundamental aspects of the study of rocks. Georg Bauer published Concerning Metallic Things in 1556. By 1785, the British geologist James Hutton published Theory of the Earth, in which he explained his observations of rocks in Great Britain and his conclusion that Earth is much older than previous scientists before him had guessed. Geologists are scientists who study the earth and rocks, distinguish three main groups of rocks: igneous rocks, sedimentary rocks, and metamorphic rocks.
These distinctions are made on the basis of the types of minerals in the rock, the shapes of individual mineral grains, and the overall texture of the rock, all of which indicate the environment, pressure, and temperature in which the rock was made. Igneous rocks form when magma is below the land of the Earth or lava at the land of the Earth hardens. The minerals in the rock will make crystals or grow together so that the separate crystals make 1 crystal altogether. Igneous rocks and magma make up much of the oceanic and continental crust, as well as most of the rock deeper in the Earth.
Igneous rocks can be identified by the interlocking appearance of the crystals in them. Typical igneous rocks do not have a layered texture, but exceptions exist. For example, in large bodies of igneous rock, relatively thick crystals that are made early can sink to the bottom of the magma, and less thick layers of crystals that are made later can accumulate on top. Igneous rocks can form deep within the Earth or at the surface of the Earth in volcanoes.
In general, igneous rocks that form deep within the Earth have large crystals that indicate a longer period of time during which the magma cools. Igneous rocks that form at or near the surface of the Earth, such as volcanic igneous rocks, cool quickly and contain smaller crystals that are difficult to see without magnification. Obsidian, also called volcanic glass, cools down so fast that no crystals are made. Nevertheless, obsidian is considered to be an igneous rock.
Igneous rocks are classified on the basis of how much minerals there are and the size of the crystals in the rock. Extrusive igneous rocks have small crystals and crystallize at or near the Earth’s surface. Intrusive igneous rocks cool slowly below the Earth’s surface and have larger crystals. Rocks made up of thick, dark-colored minerals like olivine, pyroxene, amphibole, and plagioclase are called mafic igneous rocks.
Light-colored, less thick minerals, including quartz, mica, and feldspar are called felsic igneous rocks. Common igneous rocks include the felsic igneous rocks granite and rhyolite, and the mafic igneous rocks gabbro and basalt. Granite is an intrusive igneous rock that includes large crystals of the minerals quartz, feldspar, mica, and amphibole that form deep within the Earth. Rhyolite includes the same minerals, but forms as extrusive igneous rock near the surface of the Earth or in volcanoes and cools quickly from magma or lava, so its crystals are difficult to observe with the naked eye.
Similarly, gabbro is more coarse-grained than basalt and made deeper down in the Earth, but both rocks include the minerals pyroxene, feldspar, and olivine. Fabulous exposures of igneous rocks occur in the volcanoes of Hawaii, volcanic rocks of Yellowstone National Park are located in Wyoming, Idaho, Montana, in Lassen Volcanic National Park and Yosemite National Park in California. Sedimentary rocks are those made of grains of preexisting rocks or organic material that, in most cases, have been eroded, deposited, compacted, and cemented together. They typically form at the surface of the Earth as sediment moves as a result of the action of wind, water, ice, gravity, or a combination of these.
Sedimentary rocks also form as chemicals precipitate from seawater, or through accumulation of organic material such as plant debris or animal shells. Common sedimentary rocks include shale, sandstone, limestone, and conglomerate. Sedimentary rocks typically have a layered appearance because most sediments are deposited in horizontal layers and are buried beneath later deposits of sediments over long periods of time. Sediments deposited rapidly, however, tend to be poorly layered if layers are visible at all.
Sedimentary rocks are made in many different environments at the surface of the Earth. Eolian, or wind blown, sediments can accumulate in deserts. Rivers carry sediments and deposit them along their banks or into lakes or oceans. Glaciers make unusual deposits of a wide variety of sediments that they pick up as the glacier expands and moves; glacial deposits are well exposed in the northern United States. Sediments can travel in currents below sea level to the deepest parts of the ocean floor.
Secretion of calcium carbonate shells by reef-building organisms produce large quantities of limestone. Evaporation of seawater has resulted in the formation of widespread layers of salt and gypsum. Swamps rich in plants can produce coal if organic material accumulates and is buried before aerobic bacteria can destroy the dead plants. Sedimentary rocks are classified on the basis of the sizes of the particles in the rock and the composition of the rock.
Clastic sedimentary rocks comprise fragments of preexisting rocks and minerals. Chemical precipitates are sedimentary rocks that are made by precipitation of minerals from seawater, salt lakes, or mineral-rich springs. Organic sedimentary rocks formed from organic matter or organic activity, such as coal and limestone made by reef-building organisms like coral. Grain sizes in sedimentary rocks range from fine clay and silt to sand to boulders.
The sediment in a sedimentary rock reflects its environment of deposition. For example, wind-blown sand grains commonly is evidence of abrasion of their surfaces as a result of colliding with other grains. Sediments transported long distances tend to decrease in size and are more rounded than sediment deposited near their precursor rocks because of wearing against other sediments or rocks. Large or heavy sediments tend to wear out of water or wind if the energy of the water or wind is insufficient to carry the sediments.
Sediments deposited rapidly as a result of slides or slumps tend to include a larger range of sediment sizes, from large boulders to pebbles to sand grains and flakes of clay. Such rocks are called conglomerate. Along beaches, the rhythmic activity of waves moving sediment back and forth produces sandstones in which the grains are well rounded and of similar size. Glaciers pick up and carry a wide variety of sediments and often scratch or scrape the rocks over which they travel.
Sedimentary rocks are the only rocks in which fossils can be preserved because at the elevated temperatures and pressures in which igneous and metamorphic rocks form, fossils and organic remnants are ruined. The presence of fossils and the types of fossil organisms in a rock provide clues about the environment and age of sedimentary rocks. For example, fossils of human beings are not present in rocks older than approximately two million years because humans did not exist before then. Similarly, dinosaur fossils do not occur in rocks younger than about 65 million years because dinosaurs became extinct at that very time.
Fish fossils in sedimentary rock indicate that the sediments that make up the rock were deposited in a lake, river, or marine environment. By establishing the environment of the fossils in a rock, scientists learn more about the conditions under which the rock formed.
Spectacular exposures of sedimentary rocks include the Grand Canyon which is in Arizona, the eolian sandstones of Zion National Park which is in Utah, the limestones of Carlsbad National Park which is in New Mexico, and glacial features of Voyageurs National Park which is in Minnesota. Metamorphic rocks are named for the process of change that affects rocks. The changes that make metamorphic rocks usually include rises in the temperature (generally to 392°F) and the pressure of a precursor rock, which can be igneous, sedimentary, or metamorphic, to a degree that the minerals in the rock are no longer stable. The rock might change in mineral content or appearance, or even both. Clues to identifying metamorphic rocks include the presence of minerals such as mica, amphibole, staurolite, and garnet, and layers in which minerals are aligned as a result of pressure applied to the rock.
Common metamorphic rocks include slate, schist, and gneiss. Metamorphic rocks commonly are made in mountains such as the Appalachian Mountains, parts of California, and the ancient, eroded metamorphic rocks in the Llano Uplift of central Texas. Metamorphic rocks are classified depending on their constituent minerals and texture. Foliated metamorphic rocks are those that have a layered texture. In foliated metamorphic rocks, elongate or platy minerals such as mica and amphibole become aligned as a result of pressure on the rock. Foliation can range from alternating layers of light and dark minerals typical of gneiss to the seemingly perfect alignment of platy minerals in slate.
Some metamorphic rocks aren’t foliated and have a massive texture devoid of layers. Mineralogy of metamorphic rocks reflects the mineral content of the precursor rock and the pressure and temperature at which metamorphism occurs. As sediments undergo metamorphism, the layers of sediment can be folded or become more pronounced as pressure on the rock increases. Elongate or platy minerals in the rock tend to become aligned in the same direction.
For example, when shale metamorphoses to slate, it becomes easier to split the well-aligned layers of the slate into thin, flat sheets. This property of slate makes it an attractive roofing material. Marble-metamorphosed limestone typically does not have the pronounced layers of slate, but is used for flooring and sculptures.
Metamorphism of igneous rocks can cause the different minerals in the rocks to separate into layers. When granite metamorphoses into gneiss, layers of light-colored minerals and dark-colored minerals form. As with sedimentary rocks, elongate or platy minerals become well-aligned as pressure on the rock increases.
As sediments undergo metamorphism, the layers of sediment can be folded or become more pronounced as pressure on the rock increases. Elongate or platy minerals in the rock tend to become aligned in the same direction. For example, when shale metamorphoses to slate, it becomes easier to split the well-aligned layers of the slate into thin, flat sheets. This property of slate makes it an attractive roofing material.
Marble-metamorphosed limestone-typically does not have the pronounced layers of slate, but is used for flooring and sculptures. Metamorphism of igneous rocks can cause the different minerals in the rocks to separate into layers. When granite metamorphoses into gneiss, layers of light-colored minerals and dark-colored minerals are made. As with sedimentary rocks, elongate or platy minerals become well-aligned as pressure on the rock increases.
It is possible for metamorphic rocks to change into other metamorphic rocks. In some regions, especially areas where mountain building is taking place, it is not unusual for several episodes of change to affect rocks. It can be difficult to unravel the effects of each episode of metamorphism. The word igneous comes from the Latin word ignis which means of fire. Sedimentary rocks make layers at the bottoms of oceans and lakes.