time needed for one half of the mass of a sample of a radioactive isotope to decay ?
100
asthenosphere
the plasticlike layer of earth on which the lithosphere plates float and moved around
100
tsunami
powerful seismic sea that begins over an ocean floor
200
prasedymium
59th in the periodic table
200
tundra
treeless biome
200
alpha particles
consists of a particle containing two protons and two neutrons
200
continental drift
Wegener's hypothesis that all continents were once connected in a single large landmass that broke apart about 200 million years ago and slowly drifted to their current position
200
earthquake
movement of the ground that occurs when rock inside Earths pass and elastic limit
300
californium
98th in periodic table
300
desert
warm area with a lot of sand
300
element
substance that cannot be broken into simpler substances
300
convection current
current in earth's mantle
300
lava
molten rock flowing onto Earths surface
400
helium
2nd in periodic table
400
wetlands
are regions are wet most of the year
400
electron
What is negatively - charged particle that exists in an electron cloud formation around an atoms nucleus
400
lithosphere
rigid layer on Earth about 100 km thick , made of the earths crust and a part of the upper mantle
400
rift
long crack
500
vandium
23rd one in periodic table
500
temperate rain forest
warm wet weather
500
proton
positively charged particle in the nucleus of an atom
500
pangea
all land put together
500
volocano
cone-shaped hill or mountain formed when magma , solids , and gas erupt on onto Earths surface through a vent