Clues to the Earth`s Past

1. Fossils:
are the remains, imprints, or traces of prehistoric organisms.

2. Permineralized remains:
are fossils in which the spaces inside are filled with minerals from groundwater.

3. Carbon film: 

a thin film of carbon residue is left, forming a silhouette of the original organism.

4. Mold:

the hard part might decay or dissolve, leaving behind a cavity in the rock.

 

5. Cast:

a type of body fossil that forms when crystals fill a mold or sediments wash into a mold and harden into rock.

6. Index fossils:

are the remains of species that existed on Earth for relatively short periods of time, were abundant, and were widespread geographically.

7. Principle of superposition: 

states that in undisturbed rock layers, the oldest rocks are on the bottom and the rocks become progressively younger toward the top.

8. Relative age: 

the age of something compared with the other things.

9. Unconformity:

gap in the rock layer that is due to erosion or periods without any deposition.

10. Absolute age:

is the age, in years, of a rock or other objects. 

11. Radioactive decay:

process in which some isotopes break down in other isotopes and particles.

12. Half-life:

time it takes for half of the atoms of an isotope to decay.

13. Radiometric dating:

process used to calculate the absolute age of the rock by measuring the ratio of parent isotope to daughter product in a mineral and knowing the half-life of the parent.

14. Uniformitarianism:

principle stating that Earth processes occurring today are similar to those that occurred in the past.

 

Water Erosion and Deposition

1. Runoff:
water that doesn´t soak into the ground or evaporate but instead flows across Earth´s surface.
                                    
2. Channel:
water moving down in the same path that creates a groove.
                                    
3. Sheet erosion:
occurs when water that is flowing as sheets picks up and carries away sediment.

4. Drainage basin:
is the area of land from which a stream or river collects runoff.

5. Meander:
broad, c-shaped curve in a river or stream, formed by erosion of it´s outer bank.

6. Groundwater:water that soaks into the ground and collects in pores and empty spaces.      

7. Permeable:
describes soil and rock with connecting pores through which water can flow.

8. Impermeable:
describes materials that water cannot pass through.

9.Aquifer:
a layer of permeable rock that lets water move freely. 

10. Water table:
upper surface of the zone of saturation.

                   

11. Spring:
forms when water table meets Earth´s surface.

12. Geyser:
is a hot spring that erupts periodically, shooting water and steam into the air.

13. Cave:
underground opening that can form when acidic ground water dissolves limestone.

14. Long-shore current:
current that runs parallel to the shoreline, is caused by waves colliding with the shore at slight angles,and moves tons of loose sediment.

     

15. Beaches:
are deposits of sediment that are parallel to the shore.