Radiometric dating volcanic ash dating online servies
Blocks weighing up to 1,000 tonnes were hurled 100 m (330 feet).
However, the most violent explosions occurred on 19 February 1975, accompanied by what eye-witnesses described as atmospheric shock waves.9 Blocks up to 30 m (100 ft) across were catapulted up to 3 km (almost 2 miles). Turbulent avalanches of ash and blocks swept down Ngauruhoe’s sides at about 60 km (35 miles) per hour.10 It is estimated that at least 3.4 million cubic metres (120 million cubic feet) of ash and blocks were ejected in 7 hours.11up If any of these assumptions are violated, then the technique fails and any “dates” are false.
Afterwards, Ngauruhoe steamed almost continuously, with many small ash eruptions8 (Figure 5).
Cannon-like, highly explosive eruptions in January and March 1974 threw out large quantities of ash as a column into the atmosphere, and as avalanches flowing down the cone’s sides.
The potassium-argon (K–Ar) dating method is often used to date volcanic rocks (and by extension, nearby fossils). Eleven samples were collected from five recent lava flows during field work in January 1996—two each from the 11 February 1949, 4 June 1954, and 14 July 1954 flows and from the 19 February 1975 avalanche deposits, and three from the 30 June 1954 flow14 (Figure 6).
In using this method, it is assumed that there was no daughter radiogenic argon (Ar*) in rocks when they formed.13 For volcanic rocks which cool from molten lavas, this would seem to be a reasonable assumption. Inset: Andesite of the June 30, 1954 flow, Mt Ngauruhoe, seen at 60 times magnification under a geological microscope. The darker recent lavas were clearly visible and each one easily identified (with the aid of maps) on the northwestern slopes against the lighter-coloured older portions of the cone (Figures 4 and 7).
Most scientists today believe that life has existed on the earth for billions of years.
This belief in long ages for the earth and the existence of life is derived largely from radiometric dating.
It is not as well publicized as its larger close neighbour MT Ruapehu, which has erupted briefly several times in the last five years.
Fossils are almost never dated by radiometric methods, since they rarely contain suitable radioactive elements.
A common way of dating fossils (and rocks which do not contain radioactive elements) is by “dating” an associated volcanic rock. It depends on the rate at which radioactive potassium decays into the gas argon.
However, Mt Ngauruhoe is an imposing, almost perfect cone that rises more than 1,000 metres (3,300 feet) above the surrounding landscape to an elevation of 2,291 m (7,500 feet) above sea level1 (Figure 3).
Eruptions from a central 400 m (1,300 foot) wide crater have constructed the cone’s steep (33°) outer slopes.
Yet they yield “ages” up to 3.5 million years which are thus false.