Goldfish Learn To Drive

Scientists have underestimated 
the threat of volcanic avalanches
Avalanches of ash, gas and rock that 
cascade downhill during volcanic erup-
tions may be even more dangerous than 
scientists had realized.
Pulses of high pressure form within 
these slides, called pyroclastic flows, as a 
result of turbulence, researchers report 
December 15 in 
Nature Communications
. 
Those pressures can be far stronger than 
previously estimated.
Conventional hazard assessments 
probably drastically underestimate the 
destructiveness of some pyroclastic flows, 
says volcanologist Gert Lube of Massey 
University in Palmerston North, New Zea-
land. Assessments might suggest a flow 
will only burst windows, “when actually, 
the pressures are so strong, they knock 
down the walls of the building,” he says.
Due to pyroclastic flows’ violent nature, 
researchers often have to estimate pres-
sures using computer simulations based 
on deposits left by past flows. For a more 
direct assessment, Lube and colleagues 
reproduced smaller versions of the flows 
in experiments. The team also analyzed 
the first measurements of pressures in 
natural flows, collected in 2019 when New 
Zealand’s Whakaari volcano erupted, and 
flows engulfed infrasound sensors. 
Pressures in the flows oscillated rhyth-
mically, as volcanic particles clustered 
into cascading waves and trains of rolling 
eddies. These pressure pulses would 
successively damage obstacles like blows 
from a jackhammer, Lube says. The pulses 
sometimes smashed more than three 
times as hard as average estimates in 
conventional simulations. 
— Nikk Ogasa 
HUMANS & SOCIETY
Homo sapiens
 fossils in East Africa 
get pushed further back in time
Fossils of the oldest known 
Homo sapiens
individual in East Africa are more ancient 
than previously thought.
A partial 
H. sapiens
skull and associ-
ated skeletal parts found in 1967 near 
Ethiopia’s Omo River date to at least 
233,000 years ago, pushing back the age 
of the fossils, known as Omo 1, by 36,000 
years or more. An age well exceeding 
200,000 years fits with recent discoveries 
suggesting that 
H. sapiens
evolved across 
Africa starting about 300,000 years ago 
(
SN: 7/8/17 & 7/22/17, p. 6
).
A volcanic eruption about 233,000 
years ago left a layer of ash atop the 
sediment that yielded Omo I, say volca-
nologist Céline Vidal of the University of 
Cambridge and colleagues. That ash layer 
has a chemical fingerprint matching that 
of a volcanic crater 350 kilometers north-
east of the fossil site. Dating of hardened 
ash at the volcanic crater led to the new 
minimum age estimate for the fossils, the 
scientists report January 12 in 
Nature
.
Another ash layer lying near the fossil-
bearing sediment, but with uncertain ori-
gins, provided the previous age estimate 
of about 197,000 years old. 
— Bruce Bower 
ATOM & COSMOS