The analytical equipment used to determine the abundances of isotopes is more accurate in determining ratios of isotopes than their absolute abundances.
Therefore, Sr as the y-axis would allow the isotope ratios of all rocks in a lava flow to be plotted. Damon, "K-Ar Age of Lava Dam in the Grand Canyon," Geological Society of America Bulletin, 79 (Jan.
Actually, the present lava dome at Mount St Helens is the third dome to form since the 1980 eruption, the previous two having been blasted away by the subsequent eruptions.
The current dome started growing after the volcano’s last explosive eruption on 17 October 1980.
These flows are still distinguishable today on the northwestern and western slopes of Ngauruhoe (Figure 4).Do analyses of the radioactive isotopes of rocks give reliable estimates of their ages? That is a good question, which ordinarily requires a lengthy and technical answer. Standing roughly in the centre of New Zealand’s North Island, Mt Ngauruhoe is New Zealand’s newest volcano and one of the most active (Figures 1 and 2).It is not as well publicized as its larger close neighbour Mt Ruapehu, which has erupted briefly several times in the last five years.
In order to give an initial response, we might confine our attention to dating of lava flows, the most easily dated rocks, and limit our discussion to the Grand Canyon, which contains thoroughly studied lava flows profoundly relevant to the creation/evolution question.