Geology Lab Final- All notecards

• numeric chronology/dating

• The science of determining the relative age of rocks, fossils, and geological events in actual years 

• absolute dating

• Determines the specific age or range of a fossil, rock, artifact rather than just relative age 

• radiometric chronology

• Technique used to determine absolute age of rocks, fossils, etc., by measuring the decay of radioactive isotopes  

• Radionuclide

• Unstable atoms that emit ionization radiation as they decay 

• stable nucleus

• Does not spontaneously undergo radioactive decay

• radioactive decay

• The constant process by which unstable radioactive isotopes (the parent) turn stable (daughter)

• decay rate

• The speed at which radioactive decay happens (loses particles)

• Half-life

• The predictable and constant amount of time it takes for half of the parent isotope in a sample to decay 

• Parent

• The starting isotope - the radioactive one

• Daughter

• The end isotope post-decay

What rock type is best for radiometric dating

Igneous- they come right out of the volcano

• Calcium carbonate

• Odorless white powder, colorless crystal found in rocks like limestone, insoluble in water, hardness of 3, decomposes at high temperatures

• Calcite, shells, micro-skeletons 

• Hydroxyapatite

• High osteoconductivity, similar to hard tissue 

• Makes up the primary mineral component of human bone and tooth enamel, and apatite 

• Opaline silica  

• Appears in volcanic settings, acts as a biosignature for life 

• Non-crystalline structure, high porosity, formation via fluid alteration, or biogenic processes 

• Quartz, micro-skeletons, tests (internal shells), other shells

• Chitin 

• Found in shells and organic exoskeletons

• High mechanical strength, insolubility in water and common organic solvents, biocompatibility, biodegradable

• Cellulose 

• Composes plant cell walls, found also in wood and cotton

• High tensile strength, insoluble in water, biodegradable

• Preservation without alteration

• Preserved and nothing changes 

• Recrystalization 

• Unstable skeletal minerals change into more stable mineral form (often calcite) 

• Has same chemical composition, often losing fine details 

• Mineralization

• Minerals from groundwater precipitate into the pores of buried organic matter (bones, shells, woods) 

• Replacement

• Inorganic minerals completely replace original hard organic parts of an organism 

• Creating a replica composed of new minerals while sometimes preserving internal structures

• Carbonization 

• Process where buried organisms are subjected to extreme pressure over time, foreign out volatile compounds and leading behind thin carbon film 

• Black silhouette of soft tissues, plants, insects, etc

• Molds and Casts 

• Three dimensional impressions that preserve the surface contours of ancient organisms, formed when remains are buried in sediment and dissolve 

• Hollow impression left in a rock or a filled in replica formed when sediments/minerals filled the mold 

• Soft Body Preservation

• Rare fossils where the soft tissue (muscle, organs, skin, etc.) are preserved rather than just the bones 

• Require specialized rapid burial in oxygen-free environment (often times swamps) 

Body Fossil

a part of the body of the animal / organism

Trace fossil

Something that the animal or organism left behind

Asymmetrical

line cannot be drawn for mirror image

Bilateral symmetry

animal can be divided into two mirror parts

Pentameral

Animal can be divided into five equal parts

ex: starfish

Radial

Circular Symmetry

Rock formation

significant exposure of rick, sculpted by weathering, erosion into unique shapes

Augen Genesis

high-grade metamorphic rock characterized by large, eye shaped feldspar, embedded in foliated, schistose matrix

Augen Genesis

speckled black and white rock made of feldspar, biotite, quartz

Pyrite (mafic)

Black and green, made up of pyroxene, olivine, amphibole

Granite (felsic)

white and grey, made of feldspar, quartz, fluorite

Superposition

oldest rocks are always at the bottom

original Horizontality

every sedimentary rock is put into horizontal layers

lateral continuity

rocks are deposited as a continuous lateral sequence in all directions

cross-cutting relationships

a layer has to exist before it can be cut or altered

Inclusion

Inclusions must be older than the rock they’re incorporated in