1. On the basis of mineralogical composition: Since the relative amounts of the various minerals in a rock can be measured or estimated with a fair degree of accuracy, this criteria is given more emphasis for the classification of igneous rocks. The minerals occurring in igneous rocks may be classed as (a) Essential, (b) Accessory, and (c) Secondary. The first two are the products of magmatic crystallisation whereas the third one is formed by the alteration of the primary minerals, i.e. (the 1st two), through the processes of weathering, metamorphism etc.
a. strain buildup only b. location of foci c. magnitude of P-waves [pic] d. reoccurrence rates of earthquakes in an area and the rate of strain buildup 2. What are most earthquakes associated with? a. rift valleys b. mid-ocean ridges c. divergent plate boundaries [pic] d. plate boundaries 3. At what point in the graph would a rock be permanently deformed? [pic] a. at the start of the stress [pic] b. past
J. Subbiondo © 2004The CrustThe outer layer of the Earth is called the crust. It is made up of rock that floated to the surface when the Earth was formed. It is not a continuous layer, but is made up of large masses called tectonic plates.These plates drift slowly across the Earth's surface (tectonic means moving).The movement of these plates creates mountains and valleys.At weak points in the crust, it causes volcanic eruptions. And when plates bump into each other, earthquakes occur -- emitting shock waves or vibrations called seismic waves. The crust is the Earth's coldest layer.
Stromatolites Stromatolites are Laminated organo-sedimentary structures formed by the trapping and binding, and/or precipitation of minerals by microorganisms. They can be thought of as microbial mats in which a rock-like layer of either sand or precipitated minerals is also present. Fossil Stromatolites are our earliest and most pervasive record of life on Earth. Although many Stromatolites are fossils, there are a number of locations on presently where Stromatolites are still forming. Stromatolites are layered structures formed in limestone due to the activity of cyanobacteria (blue-green algae) in warm shallow waters.
Weathered pieces of pre-existing rocks and organic debris make up a sedimentary rock. This is the type of rock that fossils are found in. Sedimentary rocks are classified into three separate groups: clastic, chemical, or organic. Clasitic rocks are classified by their grain size. Shale, siltstone, sandstone, and conglomerate.
The most abundant are stone meteorites which are primarily made up of silicate minerals such as olivine, pyroxene, and feldspar. As their name implies, iron meteorites are mainly composed of iron but also contain a significant amount of nickel. The rarest of the three are the stony-iron meteorites. They are a mixture of stony and metallic materials. Some basic facts of meteorites are: Meteorites are attracted to magnets.
Magri died in 1907, before the publication of the report. Following Magri's sudden death, excavation resumed under Sir Temi Zammit. The Hypogeum is an enormous subterranean structure excavated c. 2500 B.C., using cyclopean rigging to lift huge blocks of coralline limestone. Perhaps originally a sanctuary, it became a necropolis in prehistoric times. Hal Saflieni Hypogeum is a cultural property of exceptional prehistoric value.
Sedimentary Rocks The Beginning Sedimentary rocks are some of the foundations of the earth. They range from rock salt, to gypsum, slate, sandstone, limestone, and even coal. The grains of these rocks range from a coarse grain like cement, to very fine that only a microscope can see the grain. Where do these rocks come from? How are these sedimentary rocks formed?
His ideas were not fully accepted until the 1960s when the Atlantic Ocean floor was surveyed in detail and the mid Atlantic ridge was discovered. This is a range of mountains and volcanoes in the middle of the ocean. Rock that was discovered on the ocean floor was found to be younger than the rock in the continents. The magnetic alignment of rocks containing iron rich minerals was symmetrical either side of the ridge. This new evidence fitted in with the theory of continental drift.
Soft life forms without shell or anything to keep them from harm had existed. Stromatolites were among one of the early life forms that have been discovered. They are algal mats that had actually been a major part of the earths surface, breathing oxygen in to the atmosphere. It is amazing how time changes things because they are now only found in shallow water in few select places. During the Paleozoic era, may invertebrate animals existed, thriving off of the warm climate created as continents made their way closer to the equator.