



Nour Wageh / Unsplash
Colin Caprani, Monash University and Scott Menegon, Swinburne University of TechnologyThe Great Pyramid of Giza in Egypt has survived more than 4,500 years. Earthquakes have repeatedly shaken the region, including the magnitude 5.8 Cairo earthquake in 1992, which dislodged some of the pyramid’s outer casing stones. Yet the main body remained essentially intact.
How has it survived so well? A new study of the pyramid’s vibrations by Egyptian geophysicist Asem Salama and colleagues provides insight into its performance during earthquakes, and identifies some interesting features.
But we should be cautious to conclude that its impressive longevity is proof of its builders’ knowledge of earthquake engineering.
The researchers measured the pyramid’s vibrations in ambient conditions. They found that its natural frequencies – the frequencies at which it “prefers” to vibrate – are mostly between about 2.0 and 2.6 hertz (cycles per second). The surrounding soil has a much lower dominant frequency, around 0.6Hz.
Every structure has a natural rhythm. Push a child on a swing at the right moment and the motion grows; push at the wrong moment and little happens.
Buildings and monuments behave similarly. If earthquake shaking matches a structure’s natural frequency, the motion can be amplified. This is called resonance, and it can be catastrophic.
These findings suggest some behaviour that may be helpful during an earthquake, including a frequency mismatch between the pyramid and the soil. But they do not, by themselves, prove people intentionally built the pyramid to be resilient to earthquakes.
The study used a method called horizontal-to-vertical spectral ratio analysis, or HVSR. This records tiny background motions from wind, traffic, human activity and natural ground vibration.
By comparing the horizontal and vertical components of these motions, researchers can estimate dominant frequencies in the soil and structure. In this case, instruments were placed at 37 locations in and around the pyramid, including internal passages, exterior stones and nearby soil.
The method provides useful information without damage. However, it only measures the response to small background vibrations, not the severe shaking of an earthquake.
When shaking from an earthquake happens at a frequency that matches a structure’s natural frequency, it can cause resonance. Resonance can be catastrophic.
The 1940 collapse of the Tacoma Narrows bridge in the US is often attributed to resonance during high winds. WikimediaSo the measured difference matters. If the ground and the structure vibrate at different rates, the ground is less likely to feed energy efficiently into the structure.
But this addresses only one possible mechanism of earthquake damage. There are plenty of examples of structures performing poorly in earthquakes, even though there was a frequency mismatch to the soil below.
Modern earthquake design does not assess resilience from one frequency comparison.
Instead, we look at a whole list of questions. How severe is the expected shaking? What ground is the structure on? How heavy and flexible is the structure? Can the structure deform and dissipate energy without sudden collapse? How serious would failure be?
The structure’s natural period or rhythm (which is related to its natural frequency) is part of that assessment. But it sits alongside many other factors.
In practice, earthquake damage depends not only on the earthquake but on the structures that receive it. Australia’s 1989 Newcastle earthquake, for example, was not huge by global standards, but many buildings fared poorly and 13 people died.
Australia’s 1989 Newcastle earthquake wasn’t huge – but it caused great damage and 13 deaths. Australian Earthquake Engineering Society, CC BYFor the Great Pyramid, the behaviour of the stonework is especially important. Ambient vibration testing measures behaviour under very small motions. During strong earthquake shaking, masonry can crack, open joints, rock, slide and lose stiffness. Each of these changes the structure’s natural period, complicating the behaviour.
In evaluating the pyramid’s longevity, we should also consider survivorship bias.
Famously, in the second world war, statistician Abraham Wald was asked where armour should be added to aircraft. The obvious answer was to reinforce the places where returning aircraft had the most bullet holes.
Wald argued the opposite: those aircraft had survived. The aircraft that did not return were missing from the data.
This famous diagram shows the pattern of bullet holes on returning aircraft in the second world war. Martin Grandjean / McGeddon (picture) / US Air Force (hit plot concept) / Wikimedia, CC BYAncient structures pose a similar problem. We admire ancient aqueducts, temples and pyramids because they are still here. The failed structures, poor foundations, weak details and abandoned experiments are mostly gone.
That does not diminish the Great Pyramid. It simply means looking at structures that survive today does not tell us everything about the design intentions behind them.
The pyramid may not have been intentionally designed for resilience in an earthquake. But its survival is not an accident, either.
From an engineering point of view, it has many favourable features: a broad base, low centre of mass, tapering form, symmetrical plan, competent limestone foundation and massive masonry load path. It is squat, stiff and well-founded rather than tall, slender and flexible.
The safest conclusion is that the builders made excellent empirical engineering choices. Those choices may have been driven by construction experience, observation, structural necessity, or cultural intent. Their seismic benefits may be real without being the original purpose.
The Great Pyramid’s survival is not magic, and it is not proof of ancient seismic design. As evidence, this study is important and impressive, but incomplete.![]()
Colin Caprani, Associate Professor, Civil Engineering, Monash University and Scott Menegon, Senior Lecturer, Civil and Construction Engineering, Swinburne University of Technology
This article is republished from The Conversation under a Creative Commons license. Read the original article.






This was now used to transport stones to build the third layer. This process was repeated 209 times till the pyramid was finished. Then, starting from the top, the highest level of the ramp was removed, and the missing stones of level 209 were put into place to finish this level,” he added. “This reverse process of ramp removal and placement of missing stones was repeated 209 times ending in the lowest level being completed last. Because the ramp used is not an exterior ramp, nor an interior one, it is an ‘L Notch Ramp’ since it is built like a cut-out notch within the footprint of each layer of stones.”Hooda proposed that the ancient Egyptians likely used a dual “L Notch Ramp,” system for pyramid construction, with one ramp for moving stones upward and a smaller ramp for workers to descend. This method, which left no visible traces after the ramps were dismantled, helps explain the long-standing mystery of Egyptian pyramids logistics.His painstaking research also highlights evidence of this approach, such as the smaller stones used at the pyramid’s higher levels—a design compromise necessitated by the L Notch Ramp system. It also identifies eight interlocking components that form an integrated explanation for the construction, providing comprehensive proof of the method.

Global demand for critical minerals, particularly lithium, is growing rapidly to meet clean energy and de-carbonisation objectives.
Africa hosts substantial resources of critical minerals. As a result, foreign mining companies are rushing to invest in exploration and acquire mining licences.
According to the 2023 Critical Minerals Market Review by the International Energy Agency, demand for lithium, for example, tripled from 2017 to 2022. Similarly, the critical minerals market doubled in five years, reaching US$320 billion in 2022. The demand for these metals is projected to increase sharply, more than doubling by 2030 and quadrupling by 2050. Annual revenues are projected to reach US$400 billion.
In our recent research, we analysed African countries that produce minerals that the rest of the world has deemed “critical”. We focused on lithium projects in Namibia, Zimbabwe, the Democratic Republic of Congo (DRC) and Ghana. We discovered these countries do not yet have robust strategies for the critical minerals sector. Instead they are simply sucked into the global rush for these minerals.
We recommend that the African Union should expedite the development of an African critical minerals strategy that will guide member countries in negotiating mining contracts and agreements. The strategy should draw from leading mining practices around the world. We also recommend that countries should revise their mining policies and regulations to reflect the opportunities and challenges posed by the increasing global demand for critical minerals.
Otherwise, African countries that are rich in critical minerals will not benefit from the current boom in demand.
There is no universal consensus on what critical minerals are. Various regions and institutions have different lists of critical minerals, and the contents of these lists keep changing. For instance, Australia has classified 47 minerals as critical. The European Union has identified a list of 34 critical raw materials that are important to the EU economy and face a risk of disruption. The US critical minerals list contains 50 elements, 45 of which are also considered strategic minerals.
Each country or region has reasons why these minerals are classified as critical. For most western countries, minerals are critical if they
are essential for a low carbon economy or for national security
have no substitutes
are vulnerable to supply chain disruption.
At the time of our research there were 18 lithium projects at various stages, from early-stage exploration to production, across Africa. We focused on those in Namibia, Zimbabwe, the DRC and Ghana.
Our research revealed that conversations on Africa’s critical minerals had largely been shaped by geostrategic and economic opportunities arising from demand from western countries and China. Less attention was paid to the supply chains African countries should secure for current and future industrial applications.
We realised that these countries contributed little to global carbon emissions and their economies were not driven by industrialisation. The current inadequate infrastructure and policies to deal with the repercussions of lithium mining, for example, underscored the lack of a clear agenda. Lithium mining has impacts on communities, biodiversity, water sources and energy usage.
We also discovered that with over 30% of the world’s critical minerals deposits, African countries could become major global suppliers. They could also trade among themselves to avoid potential supply chain disruption or even monopoly by countries outside Africa.
Our research also highlights that emerging lithium mining in Zimbabwe, the DRC and Namibia is reinforcing and breeding new forms of corruption and illegality in the resources sector. Ghana is still in the early stage of setting up its lithium sector.
Africa needs stronger resources governance: regulations, accountability and transparency. Mining policies and regulations must reflect the opportunities and challenges of meeting global demand for critical minerals. Mining companies operating in African countries should adhere to leading mining practices and national regulations to minimise the environmental and social impacts of their operations.
The claim that it is urgent to acquire critical minerals must not be an excuse for African governments and foreign mining companies to bypass mining and environmental regulations. Rather, the urgency claims should give African governments greater power to make mining deals that will benefit people and the environment.
For these countries to use the economic opportunities arising, there must be incentives for local companies to mine and process lithium before exporting it. Processing of lithium in the country of origin would increase local returns, create jobs, and drive the growth of other sectors of the economy.
There is a need for coordinated efforts in Africa to build local capacity along the mining chain, from exploration to the market. There’s an opportunity also to build industries to support the global de-carbonisation agenda. An example would be manufacturing electronic vehicle batteries. In this way, Africa would not only be a source of raw materials, but a competitive source of low carbon products.
These are some key lessons for African countries.![]()
James Boafo, Lecturer in Sustainable Development, Murdoch University; Eric Stemn, Lecturer, Safety and Engineering, University of Mines and Technology; Jacob Obodai, Postdoctoral Research Assistant, Edge Hill University, and Philip Nti Nkrumah, Researcher, Sustainable Minerals Institute, The University of Queensland
This article is republished from The Conversation under a Creative Commons license. Read the original article.
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India’s Finance Minister Nirmala Sitharaman at the BRICS Finance Ministers and Central Bank Governors meeting in Washington, D.C. Photo: Twitter @nirmalasitharaman retweet of April 12, 2023 from Indian Ministry of Finance