Ancient_JJ Earth_NN1 's_GE Magnetic_JJ Field_NN1 Was_VBDZ Structured_VVN Like_II Today_RT 's_GE Two-Pole_NP1 Model_NN1 ScienceDaily_NP1 (_( Oct._NPM1 3_MC ,_, 2009_MC )_) --_JJ Princeton_NN1 University_NN1 scientists_NN2 have_VH0 shown_VVN that_CST ,_, in_II ancient_JJ times_NNT2 ,_, the_AT Earth_NN1 's_GE magnetic_JJ field_NN1 was_VBDZ structured_VVN like_II the_AT two-pole_JJ model_NN1 of_IO today_RT ,_, suggesting_VVG that_CST the_AT methods_NN2 geoscientists_NN2 use_VV0 to_TO reconstruct_VVI the_AT geography_NN1 of_IO early_JJ land_NN1 masses_NN2 on_II the_AT globe_NN1 are_VBR accurate_JJ ._. 
The_AT findings_NN2 may_VM lead_VVI to_II a_AT1 better_JJR understanding_NN1 of_IO historical_JJ continental_JJ movement_NN1 ,_, which_DDQ relates_VVZ to_II changes_NN2 in_II climate_NN1 ._. 
By_II taking_VVG a_AT1 closer_JJR look_NN1 at_II the_AT 1.1_MC billion-year-old_JJ volcanic_JJ rocks_NN2 on_II the_AT north_ND1 shore_NN1 of_IO Lake_NNL1 Superior_NP1 ,_, the_AT researchers_NN2 have_VH0 found_VVN that_DD1 Earth_NN1 's_GE ancient_JJ magnetic_JJ field_NN1 was_VBDZ a_AT1 geocentric_JJ axial_JJ dipole_NN1 --_NN1 essentially_RR a_AT1 large_JJ bar_NN1 magnet_NN1 centered_VVD in_II the_AT core_NN1 and_CC aligned_VVN with_IW the_AT Earth_NN1 's_GE spin_NN1 axis_NN1 ._. 
Some_DD earlier_JJR studies_NN2 of_IO these_DD2 rocks_NN2 had_VHD led_VVN other_JJ teams_NN2 to_TO conclude_VVI that_CST the_AT magnetic_JJ field_NN1 of_IO the_AT ancient_JJ Earth_NN1 had_VHD a_AT1 far_RG more_RGR complex_JJ structure_NN1 --_NN1 some_DD proposing_VVG the_AT influence_NN1 of_IO four_MC or_CC even_RR eight_MC poles_NN2 --_NN1 implying_VVG that_DD1 present_JJ models_NN2 of_IO the_AT supercontinents_NN2 that_CST relied_VVD on_II paleomagnetic_JJ data_NN and_CC an_AT1 axial_JJ dipole_NN1 assumption_NN1 were_VBDR wrong_JJ ._. 
The_AT report_NN1 ,_, which_DDQ will_VM appear_VVI in_II the_AT October_NPM1 issue_NN1 of_IO Nature_NN1 Geoscience_NP1 ,_, says_VVZ that_CST previous_JJ efforts_NN2 to_TO interpret_VVI the_AT ancient_JJ geomagnetic_JJ field_NN1 in_II rocks_NN2 from_II North_ND1 America_NP1 were_VBDR confused_VVN by_II the_AT rapid_JJ migration_NN1 of_IO the_AT continent_NN1 toward_II the_AT equator_NN1 in_II the_AT distant_JJ past_NN1 ._. 
The_AT researchers_NN2 "_" neatly_RR lay_VVD to_II rest_NN1 the_AT long-standing_JJ controversy_NN1 over_II the_AT nature_NN1 of_IO Earth_NN1 's_GE magnetic_JJ field_NN1 1.1_MC billion_NNO years_NNT2 ago_RA ,_, "_" writes_VVZ geoscientist_NN1 Joseph_NP1 Meert_NN1 of_IO the_AT University_NN1 of_IO Florida_NP1 in_II an_AT1 essay_NN1 that_CST accompanies_VVZ the_AT report_NN1 ._. 
"_" In_II this_DD1 paper_NN1 ,_, we_PPIS2 show_VV0 that_DD1 Earth_NN1 's_GE magnetic_JJ field_NN1 has_VHZ been_VBN more_RGR stable_JJ in_II the_AT past_NN1 than_CSN originally_RR believed_VVN ,_, "_" said_VVD Adam_NP1 Maloof_NP1 ,_, an_AT1 assistant_JJ professor_NN1 of_IO geosciences_NN2 at_II Princeton_NP1 and_CC one_MC1 of_IO the_AT paper_NN1 's_GE authors_NN2 ._. 
The_AT Earth_NN1 's_GE magnetic_JJ field_NN1 wraps_VVZ around_II the_AT globe_NN1 ,_, shielding_VVG life_NN1 from_II harmful_JJ cosmic_JJ rays_NN2 ._. 
It_PPH1 is_VBZ emanated_VVN by_II the_AT Earth_NN1 's_GE iron_NN1 core_NN1 and_CC is_VBZ shaped_VVN by_II a_AT1 multitude_NN1 of_IO factors_NN2 ,_, including_II the_AT spinning_NN1 of_IO the_AT Earth_NN1 and_CC circulatory_JJ motion_NN1 influenced_VVN by_II the_AT Earth_NN1 's_GE rotation_NN1 and_CC temperature_NN1 differences_NN2 between_II the_AT inner_JJ core_NN1 's_GE outer_JJ layers_NN2 and_CC the_AT lower_JJR mantle_NN1 ._. 
The_AT researchers_NN2 obtained_VVD magnetic_JJ measurements_NN2 from_II a_AT1 thick_JJ stack_NN1 of_IO lava_NN1 flows_VVZ in_II the_AT Lake_NNL1 Superior_NP1 region_NN1 ._. 
The_AT lavas_NN2 erupted_VVN when_CS geologic_JJ forces_NN2 attempted_VVD to_TO tear_VVI apart_RL central_JJ North_ND1 America_NP1 forming_VVG the_AT Keweenawan_JJ Rift_NN1 ._. 
The_AT researchers_NN2 used_VVD the_AT tiny_JJ magnetic_JJ minerals_NN2 within_II the_AT volcanic_JJ rocks_NN2 to_TO record_VVI the_AT orientation_NN1 of_IO the_AT geomagnetic_JJ field_NN1 at_II the_AT time_NNT1 the_AT rocks_NN2 erupted_VVN onto_II the_AT Earth_NN1 's_GE surface_NN1 ._. 
By_II knowing_VVG how_RRQ those_DD2 grains_NN2 pointed_VVN to_II the_AT magnetic_JJ field_NN1 of_IO that_DD1 time_NNT1 ,_, the_AT scientists_NN2 could_VM deduce_VVI the_AT latitude_NN1 where_CS they_PPHS2 were_VBDR located_VVN when_CS the_AT lava_NN1 flows_NN2 erupted_VVN and_CC cooled_VVN ._. 
The_AT grains_NN2 pointed_VVN to_II where_RRQ "_" paleo-north_ND1 "_" was_VBDZ for_IF each_DD1 rock_NN1 ._. 
Studying_VVG layers_NN2 of_IO the_AT basaltic_JJ lava_NN1 flows_NN2 ,_, they_PPHS2 used_VVD the_AT information_NN1 to_TO track_VVI how_RRQ the_AT Earth_NN1 's_GE magnetic_JJ poles_NN2 have_VH0 "_" flipped_VVN "_" over_II the_AT eons_NN2 ,_, with_IW the_AT North_ND1 Magnetic_JJ Pole_NN1 becoming_VVG the_AT South_ND1 Magnetic_JJ Pole_NN1 and_CC vice_RR21 versa_RR22 ._. 
The_AT team_NN1 studied_VVD three_MC of_IO these_DD2 reversals_NN2 that_CST occurred_VVD over_RP a_AT1 few_DA2 million_NNO years_NNT2 ._. 
The_AT scientists_NN2 plan_VV0 to_TO use_VVI the_AT data_NN to_TO better_RRR understand_VVI how_RRQ continents_NN2 moved_VVN in_II the_AT distant_JJ past_NN1 ,_, massing_VVG to_TO form_VVI supercontinents_NN2 ._. 
"_" We_PPIS2 needed_VVD to_TO be_VBI able_JK to_TO have_VHI a_AT1 working_JJ model_NN1 of_IO how_RRQ the_AT geomagnetic_JJ field_NN1 behaved_VVN in_II the_AT past_NN1 if_CS we_PPIS2 are_VBR going_VVGK to_TO talk_VVI about_II where_RRQ plates_NN2 have_VH0 moved_VVN ,_, how_RRQ fast_RR they_PPHS2 've_VH0 moved_VVN and_CC how_RGQ ancient_JJ supercontinents_NN2 were_VBDR configured_VVN ,_, "_" said_VVD Nicholas_NP1 Swanson-Hysell_NP1 ,_, a_AT1 graduate_NN1 student_NN1 at_II Princeton_NP1 and_CC the_AT first_MD author_NN1 on_II the_AT paper_NN1 ._. 
Knowing_VVG the_AT proper_JJ location_NN1 of_IO continents_NN2 is_VBZ key_JJ to_II understanding_VVG the_AT climate_NN1 of_IO any_DD era_NN1 ,_, Maloof_NP1 said_VVD ,_, because_CS the_AT shape_NN1 and_CC location_NN1 of_IO continents_NN2 affect_VV0 ocean_NN1 currents_NN2 ,_, global_JJ average_JJ temperatures_NN2 and_CC wind_NN1 patterns_NN2 ._. 
And_CC by_II understanding_VVG in_II detail_NN1 what_DDQ Earth_NN1 's_GE climate_NN1 was_VBDZ like_II in_II ancient_JJ times_NNT2 ,_, he_PPHS1 noted_VVD ,_, scientists_NN2 can_VM better_RRR comprehend_VVI the_AT climate_NN1 of_IO today_RT and_CC make_VVI more_RGR accurate_JJ projections_NN2 for_IF the_AT future_NN1 ._. 
According_II21 to_II22 scientific_JJ reconstructions_NN2 ,_, a_AT1 supercontinent_NN1 known_VVN as_II Rodinia_NP1 existed_VVD between_II 1_MC1 billion_NNO and_CC 800_MC million_NNO years_NNT2 ago_RA ._. 
The_AT extreme_JJ cooling_NN1 of_IO the_AT global_JJ climate_NN1 about_RG 700_MC million_NNO years_NNT2 ago_RA and_CC the_AT rapid_JJ evolution_NN1 of_IO primitive_JJ life_NN1 during_II subsequent_JJ periods_NN2 are_VBR often_RR thought_VVN to_TO have_VHI been_VBN triggered_VVN by_II the_AT breaking_VVG up_RP of_IO Rodinia_NP1 ._. 
Rodinia_NN1 predated_VVN a_AT1 more_RGR recently_RR created_VVN supercontinent_NN1 called_VVN Pangaea_NP1 ,_, which_DDQ came_VVD together_RL about_RG 300_MC million_NNO years_NNT2 ago_RA ._. 
Scientists_NN2 have_VH0 pieced_VVN Rodinia_NP1 together_RL by_II comparing_VVG rocks_NN2 with_IW similar_JJ geological_JJ features_NN2 that_CST are_VBR now_RT widely_RR dispersed_VVN ._. 
Knowing_VVG that_CST they_PPHS2 have_VH0 confirmed_VVN the_AT structure_NN1 of_IO the_AT Earth_NN1 's_GE magnetic_JJ field_NN1 at_II that_DD1 time_NNT1 gives_VVZ Maloof_NP1 and_CC Swanson-Hysell_NP1 the_AT confidence_NN1 to_TO learn_VVI more_RRR about_II the_AT supercontinent_NN1 and_CC that_DD1 epoch_NN1 ._. 
"_" For_IF the_AT past_JJ 30_MC years_NNT2 ,_, scientists_NN2 have_VH0 feared_VVN that_CST the_AT geometry_NN1 of_IO Earth_NN1 's_GE field_NN1 was_VBDZ complex_JJ and_CC varied_VVD ,_, "_" Maloof_NP1 said_VVD ._. 
"_" Such_DA a_AT1 complex_JJ field_NN1 made_VVD it_PPH1 very_RG hard_RR for_IF people_NN to_TO reconstruct_VVI the_AT ancient_JJ geography_NN1 of_IO the_AT planet_NN1 because_CS they_PPHS2 could_VM not_XX rely_VVI on_II a_AT1 predictable_JJ field_NN1 ._. 
We_PPIS2 show_VV0 that_CST these_DD2 fears_NN2 were_VBDR unfounded_JJ --_NN1 at_RR21 least_RR22 for_IF 1.1_MC billion_NNO years_NNT2 ago_RA --_JJ and_CC that_CST the_AT evidence_NN1 for_IF a_AT1 complex_JJ ancient_JJ field_NN1 was_VBDZ an_AT1 artifact_NN1 of_IO the_AT way_NN1 rocks_NN2 had_VHD been_VBN sampled_VVN ._. "_" 
